Finishing and Assessing EcoColumns

Finishing EcoColumns is a sad, but necessary part of EcoColumns. Students become very attached to their ecocolumns, but they start to degrade after about 6-8 weeks. Plants begin to run out of space and nutrients and will die off and while the fish do eat elodea and survive the whole time (mostly), they are omnivores (we use mostly Gambusia) and prefer to go back into the tank and eat regular fish food with some protein.

Creating graphs, analyzing data, and taking an ecocolumn test are all part of finishing ecocolumns. A document for students can be found here.


My students graph two items of data from their spreadsheets. A sample spreadsheet can be found here.  In their groups of 4, each student must graph two DIFFERENT items of data.

To graph, I allow students to choose to either hand-graph or computer-graph. Both ways are valuable. Sometimes, I will teach students to graph using Google Sheets, but this takes a class day for instruction. Other years, I will save that day by instructing kids to watch a YouTube tutorial on how to graph using Google Sheets or to just use the help function on sheets–its pretty easy now with Sheets upgrades. Many times, students will teach other students how to do it.

Hand graphing is also valuable, because kids can better read a graph on a test or in their textbooks, if they’ve spent time doing it by hand.  The AP® Exam sometimes has kids hand-drawn a graph on FRQs and it always has multiple choice questions with graphs.

Sample student graph using google sheets

Group Data Analysis

The next part of finishing ecocolumns is for students to analyze data. I provide several questions for students to discuss and answer in their groups. I give them choices for the questions as I really want them to discuss in-depth the science of what happened in their ecocolumn. My students take notes several times about the science of ecocolumns and they need to refer to their notes when answering the questions.

Students choose 2 questions to answer regarding their soil and water quality data, 2 questions about observations, adjustments, and error. In addition, they must also develop 5 follow-up questions. This is an important skill for students-to develop good questions and is NGSS Science and Engineering Practice #1. It is also AP® Science Practice #3.

Students must film the answers to their data analysis on Flipgrid.

EcoColumns on Flipgrid

The next part of finishing ecocolumns is to film on flipgrip. I’ve used flipgrid the past two years for this and really like the results. Kids get to practice their speaking skills (a common core practice), all students speak equally and there are no slackers, and students get to use props and visuals. And…I get to avoid reading more lab reports!

I give students about 90 minutes (over two days) to discuss, plan and film their flipgrid. I let them spread out so its not too noisy (I have good kids which behave). Some students film outside (we are in southern California),  some in the lab and some in my classroom.

Students preparing to film (my son is in the middle)
Students filming using the camera on a chromebook.
Students with their ecocolumn discussing before they film

Here are a couple of links to EcoColumn Flipgrids. I had permission to share on my syllabus and I also checked again with the students before I shared these videos.

Disposing EcoColumns

The next part of finishing ecocolumns is disposal. First, students put their fish back in my tanks. Some of my fish have been through multiple ecocolumns!

Fish for aquatic chambers. Gambusia (mosquito fish) are my favorite and I keep them year-round in 3 aquariums.

Next, students dump the contents of all 3 chambers in an designated natural area on campus and place the plastic chambers in bags to be recycled. We DO NOT reuse chambers for several reasons. First, I don’t have the storage area in my lab, second, they plastic typically has rips and several need duct tape after many weeks. Third, the kids really like cutting and making ecocolumns each year.

Ecocolumn basic supplies for building aren’t expensive. Ecocolumns can be successfully done without spending a lot of your science funds.

EcoColumn Test

The last part of finishing ecocolumns is a rather difficult multiple choice test at the end of the ecocolumns. This test has AP caliber questions and is challenging for students. If taught correctly, ecocolumns have A LOT of science in them. Some sample questions:

  1. What prevents your fish from dying due to ammonia in its own waste?
  •       Nitrifying bacteria turns ammonia into nitrate
  •       Nitrifying bacteria turns ammonia into Nitrogen gas
  •       Bacteria used dissolved oxygen to deactivate the ammonia
  •       Nitrogen-fixing bacteria turns ammonia into nitrites
  •       Nitrogen-fixing bacteria turns nitrogen gas into ammonia

2.  Which of the following would NOT lower pH in the aquatic chamber?

  •       Dead fish
  •       Healthy elodea
  •       Decomposing elodea
  •       Cellular respiration by the fish

I do not share out this exam or any of my exams (sorry), because unfortunately some teachers post exams (for practice) on their websites and my students will find them. It takes a lot time to develop really good questions for students that are AP® caliber.

More Ecocolumn Resources

Student directions for building ecocolumns.

Everything EcoColumns

Student handout for finishing ecocolumns

AP® is a trademark registered and/or owned by College Board, which was not involved in the production of, and does not endorse this site.


Everything Ecocolumns

My students’ favorite lab is building and taking care of Ecocolumns.  This lab gives them practice in long-term data collection and a myriad of other essential topics in APES. Here are the posts you can click on to learn how to build, buy supplies and assess ecocolumns.

Prepping Ecocolumns

Buying Supplies for Ecocolumns

Ecocolumns with a Small Budget and a Big Budget

Making Ecocolumns

The following posts are the order in which students should build ecocolumns. The fish doesn’t come for 2 weeks!

  1. Cutting and Filling Ecocolumns
  2. Planting Seeds, Setting up Data Charts, Taking Soil Data
  3. Adding Bugs, Worms and Leaf Litter
  4. Building the Aquatic Chamber
  5. Adding fish

When things go wrong

Things go wrong in ecocolumns and its okay!

Data and Assessment

Group Data Analysis
Scientific Concepts Kids Should Learn in Ecocolumns

Finishing EcoColumns

Things Go Wrong in Ecocolumns-and its OK!

Things will go wrong in ecocolumns, they always do.  And that’s part of the magic of ecocolumns. Being able to say “hmmm” or “huh, I don’t know” and being okay with the mystery.

Teach kids that its okay to fail. There is a great article about that in Scientific American.

No matter how well an ecocolumn is built, some columns will have issues.  Fish die, plants, die, fish disappear (yes, they do), plants disappear. Weird plants grow, bugs infect, they’re dropped, etc.  Its all OK. Its part of learning and discovering and as teachers, sometimes we have to say we don’t know either and leave it at that.  Read about some things they will learn, however, through ecocolumns.


(To read about building ecocolumns, go to these posts:  Student directions for building ecocolumns,   Cutting and filling bottlesplanting seeds and taking data , adding bugs, worms and leaf litter, and building the aquatic chamber.)


My kids build great ecocolumns and learn a ton, but here’s some failures from this year.

This ecocolumn had disappearing plants. Only one seed germinated and then died. So these kids had no plant data for about a month.
Volunteer grass grew in this ecocolumn. Fun to ask the kids where they think it came from. (Probably a seed picked up from leaf litter)
See the random black dots in the filter chamber? They’re all the same size and oblong. I have no idea what they are.
Dying plants. Some will die after they make their peas, and some will die from being handled too much and some just die.
Diseased leaves. I often have a black spotted disease infest bean plants. Nice way to talk about density-dependent limiting factors. Ecocolumns are close together so diseases spread more easily.
More diseased leaves
Some soil never drains very clear so kids will water the plants and drain into a plastic beaker for the entirety of the lab.

And of course, fish will die. I do a lot to prevent this, but it still happens.

Hard to see, but there’s a dead fish in the above picture (bottom right).
Burying a fish in the terrestrial chamber

And theres more for which I don’t have pictures. Over the years, I’ve had

  • Fish that jump out of the ecocolumn and die
  • Infestation with ants
  • Infestation with aphids
  • Seeds that never grow
  • Fish that devour elodea in a couple of days.

And more. Its all okay. Its still super fun for the kids.

10 Scientific Concepts Learned from Ecocolumns

Ecocolumns can teach the kids A LOT of scientific concepts if you are purposeful with the learning. If not, the kids just enjoy growing plants and having a fish and this is not worth the class time it takes.

Make sure you take the time to lecture or allow for inquiry discussions about the scientific processes in an ecocolumns. Students can take observations and make inferences, but you will need to teach them about some of the indirect processes going on (such as nutrient cycling).

Free download of Ecocolumn directions with pictures.  For more about ecocolumns, use the drop -down menus above.

10 Scientific Concepts in Ecocolumns

  1. Data collection, graphing and analysis. The more the kids take data and see patterns over time, the better the kids are able to answer these types questions on the AP® Exam.  The AP® Exam is 2/3 higher level thinking and will have data-set analysis.  In order to give my students more lab time, I flip my class.

    Student data on Google Sheets.  Students can also take data by hand. At the end of ecocolumns, students will graph their results and explain how and why numbers changed over time.
  2. Nutrient Cycling. Direct kids to see how the nitrogen cycle, carbon cycle, phosphorus cycle and water cycle are implemented in the ecocolumn. Kids really can’t figure this out on their own through inquiry so its best to have direct instruction in this (even though I’m a huge inquiry fan). Dead fish provide a great learning opportunity if you bury it in the soil.
  3. Nitrogen Cycle. Big emphasis on this cycle which is hugely important in this class and on the AP® Exam. Nitrogen fixation with the legumes, fish waste (ammonification) and then nitrification with beneficial bacteria.
  4. Limiting Factors. Plants will soon run out of space and decline. Fish could run out of dissolved oxygen if they’re too big for the chamber or if the kids put in too many.

    These plants are experiencing limiting factors. By their yellowing leaves, they may be running out of nitrogen or perhaps root space. They also have diseased leaves which is a density-independent limiting factor.
  5. Decomposition and Detritivores and Leaf Litter. I favor a filter chamber instead of a decomposition chamber, but we add worms and other detritivores to the terrestrial chamber to teach them about decomposition. My students don’t live in a forest (we live in Chaparral) so they don’t know about leaf litter–this is how they learn.  
  6. Water treatment and wastewater treatment. The filter chamber mimics one step in water treatment and is also tertiary wastewater treatment.
  7. Food Web. Elodea or duckweed eaten by the fish. Pests that find the ecocolumn and eat the plants.
  8. Water Quality:  Temperature, pH, Dissolved Oxygen, Nitriates. Students will see how they change (or don’t change) over time and may begin to see patterns.

    Dissolved oxygen probe and student taking data on their spreadsheet.
  9. Soil Quality: Temperature, pH, fertility (NPK). Kids can see how soil quality changes (or doesn’t change) over time.  You will need to guide them to why each test is important. They can also learn about soil structure, leaching, tannins, drainage etc.
  10. Eutrophication and BOD. If you have a dissolved oxygen probe or test kit (I highly recommend buying a dissolved oxygen probe if you have some funds). This is a common topic on the AP® exam and there is no better way for students to understand BOD (Biological Oxygen Demand), eutrophication and other issues than to measure DO over time. I like the Milwaukee MW600 LED Economy Portable Dissolved Oxygen Meter.


Ecocolumns with a Small Budget and with a Big Budget

Sometimes new teachers panic when they see all the shiny probes, grow lights and data measuring stuff that veteran teachers have.  Don’t worry…most of us started out with limited supplies also.  Ecocolumns can be done cheaply or expensively.  Most teachers start off cheaply and the kids still learn a ton and have lots of fun.

Student directions for building ecocolumns.

To read about building ecocolumns, go to these posts: Cutting and filling bottlesplanting seeds and taking data , adding bugs, worms and leaf litter, and building the aquatic chamber.

Read about where to find funding for supplies.

Cheap Supplies

Basic supplies for building ecocolumns are fairly inexpensive. You can read more about supplies here. 

Bottles: Ask students to bring in or ask your staff to bring you empty bottles as they use them. Bottles can be re-used, but the plastic does get wrinkled and torn so its best to start new if you can.

Sand and gravel are cheap at the garden/hardware store. You could have kids collect small rocks for gravel instead of buying.

Get construction gravel. These were $3.50/bag

Soil: You can use native soil that you dig up if you don’t want to purchase potting soil. Make sure you plant native plants/seeds if you do, because they’re adapted for that particular soil.

Colanders for rinsing gravel or rocks. I bought mine at the dollar store for $1. Get one or two to share or more if you’re feeling rich.

Seeds: I purchase packets as they’re cheap, but I do get free packets on occasion. Some garden websites will give you free seeds. Check Monsanto’s education page–they will be genetically modified, but hey, they’re free and a learning opportunity.

Water plants: If you have a pond nearby, go collect some duckweed or other water plants. If not, buy elodea (called anachris) at the pet store and break the stems in half or thirds. Elodea doesn’t care and will grow.

My son collecting duckweed.

Fish: Feeder fish that are $0.10 are notoriously bad for ecocolumns, sorry. Try getting a donation of fish. I have received Gambusia from the county health department. Ask around if someone has a pond where the fish have been overbreeding.  If you have to get feeder fish, minnows/rosy reds, are better than goldfish. Or, forget fish and get small snails. The pet store will often donate as snails are pests in their tanks, but they’re awesome for us. Or, collect critters from a local pond.

Fish Tanks: Ask your kids to donate an old one that’s getting dusty in their attic or garage. I’ve never purchased a fish tank-they’ve all been donations from people wanting to get rid of them.

Windows: Use to grow plants instead of plant lights.

Plant light donation: Ask your local law enforcement for a donation of confiscated grow lights from a busted marijuana operation. My colleague, Danielle Werts, did that. Be prepared for drug dogs to go crazy, however, if they come through your school.

These are confiscated grow lights that the Sheriff department donated. Photo courtesy of Danielle Werts at Golden Valley High in Santa Clarita, CA.

Bugs: Go on a bug hunt at school or kids collect worms and detritivores on their own and bring in. 

Worms and bugs that a student collected at home.

Cheap Data for Ecocolumns

You don’t have to take every piece of data mentioned here.  Only take the data that you have equipment for.

Rulers: Measure plant height, elodea length etc. 

Thermometers: Most labs have these already and you can use to measure water temperature and soil temperature.

pH strips to measure pH of water in lieu of pH meters.  (pH meters are pretty cheap, however, on Amazon).

Observations: The kids can learn a lot with basic observations.

A little Money

Build your own plant lights:  So much cheaper than buying a set from a scientific supply company.  PVC pipe and shop lights will cost less than $50. My colleague, Laura Solarez, had her husband build her a set over last summer. You can also ask the wood shop teacher (if you have one) or a parent to build if you buy the supplies.

Plant lights made with PVC pipe and a shop light. You can buy grow bulbs at the hardware store too. Photo and set up courtesy of Laura Solarez at West Ranch High in Santa Clarita, CA

Nitrate Test Strips: Use a few times during the lab depending on your budget.  They’re about $18-20 for a bottle of 50, but wait! I found out last year from some smart teachers that you can slice in half and increase to 100 per bottle! You use one strip per ecocolumn and you don’t have to take nitrate data every time. These strips have served me well for years Industrial Test Systems 480009 WaterWorks Nitrate/Nitrite Nitrogen

This picture shows a whole strip, but now I have student service cut in half for me length-wise to double the amount of strips.

pH probe: $15-20 on Amazon. Its worth it as it shows pH to the tenth place so it can help kids see minor changes. Kids can rotate probes so you can start with one or two probes.  Probes, however, break easily or fall out of calibration. You may want to use pH strips instead.

Dissolved oxygen kit: $40-60. This is an important reading which helps kids really understand aquatic ecosystems. For large classes over multiple years, a probe is more economical, but to start, you can go with a kit.

Dissolved Oxygen Probes are expensive, but VERY worth it.

Soil Probes or Soil Testing Kit: $25 on Amazon. Kids can pass probes and kits around so you can start with one or two and then build up supplies over time. Soil Probes are on this link.

Expensive Supplies to Buy Over Time (or if you are blessed with an awesome budget)

I love all my plant lights, probes, fish tanks etc., but it took 10 years to get all of this stuff.  I purchased a little at a time using DonorsChoose, PTA grants, Education Foundation grants, and plain old science budget money.

Dissolved Oxygen Probe/s:  The most important item to splurge on when you get some money. Kids really see patterns and changes regarding DO and this is a topic that is a big part of our exam.  I rotated 1 probe around to different groups when I first started, then built up my supply to 3 probes between 9 groups and now I’m up to 5 probes to rotate between 9 groups. Again, this took several years to get this many.  I like the Milwaukee MW600 LED Economy Portable Dissolved Oxygen Meter, because they last a long time and rarely need calibration.

Grow Lights: If you have some money, the pre-made grow lights are nice. They come with trays and a cover for humidity.

Fish Tanks, Filters and Food to keep a breeding stock of fish.

Gambusia (mosquito fish) are my favorite and I keep them year-round in 3 aquariums.

Buy more probes so not as many groups have to share. It will speed up the data process.  I now have one soil probe per group and one pH, temperature, and DO probe per two groups. Data takes 10-15 min a week this way.

I have enough probes for one of each per two groups. But, one per 3 or 4 groups is fine too. Readings take only a minute.
I have one soil probe per group now, but I didn’t even take soil data for several years.

Building the Aquatic Chamber in Ecocolumns

After two weeks of draining your ecocolumns, its time to build the aquatic chamber.  DO NOT RUSH this step.

No fish for two more days!

Student directions for building ecocolumns.

Read about buying supplies, cutting and filling bottles, planting seeds and taking data,  adding detritivores and leaf litter in previous posts.

Why its Important to Wait

Draining the ecocolumn once every day or two is extremely important to prevent fish death.  Potting soil contains silt and sand contains dust-both of which will clog fish gills.  The more you drain, the cleaner the water becomes as you flush these particles out.  The water may still be slightly orange/brown after two weeks, but this is mainly due to tannins in the soil rather than silt.

I usually send one student from each group into the lab to empty out the old water and fill the ecocolumn from the top to drain until the next day. This takes about 5 minutes.

Build the Aquatic Chamber

This is a fairly easy chamber to build. Also have students continue to take other data–plant height, soil measurements (optional).

I have a video on how to build the aquatic chamber or just keep scrolling down to the pictures and explanation.

First they need to clean some gravel. You can use aquarium gravel, but its really expensive. We use construction gravel that costs $3.50 for 50 lbs. But, its filthy so kids have to clean it.

I found colanders for $1 each at the dollar store.
Washing the graving

Next, students add purified water. I have kids “donate” the water from their original bottles in these buckets and keep for two weeks.  Its not as good as distilled, but its better than me spending a week making liters and liters using our building’s distiller.

Students take water quality measurements (see below) and then add a sprig of elodea.  They measure the length each time we do data. Elodea is the cheapest water plant at the pet store (called Anachris there). Its also available to order from scientific supply companies. Duckweed also works well, but I don’t often have a steady supply here in Southern California.

I usually buy elodea at the pet store (call ahead to see if they have “anachris” in stock) or order and have delivered.  While I’ve never ordered elodea from Amazon, I see that they have it. 3 Bundles Anacharis “Egeria Densa” Elodea Live Aquarium Plants

The elodea in the middle container came from my fish tank. It had been in the tank since last May and was to feed my Gambusia fish over the summer. The fish didn’t end up eating it (the custodian fed all summer) and became lush and green.
Measuring the length of elodea.
The finished aquatic chamber.
On the board to discuss.

Make sure students leave enough space for air to flow through and that there are holes cut in two sides. This will allow for enough dissolved oxygen and prevent fish death.

NO FISH FOR TWO MORE DAYS! Dust from the gravel needs to settle or it can kill the fish by clogging their gills and nitrifying bacteria need to colonize the water.

Taking Water Quality Measurements

First, use what you have. I’ve built up my collection of probes over 10 years using various grants. You won’t have this much to start and neither did I. Probe readings take only one minute so students can pass around and share.

Last year, I made laminated instruction sheets for each probe and then kicked myself for not thinking of the idea years ago.

You can also use water quality testing kits, regular thermometers, pH paper, etc. Splurge on a dissolved oxygen probe if you can beg some money.

I have enough probes for one of each per two groups. But, this isn’t necessary as students can rotate probes. Reading take only a minute or less.

I use vernier temperature probes, because I have them, but this is the expensive option. You could use a regular thermometer or temperature probe just as well and they’re cheaper.

Thermometer probe

You can use pH strips or pH probes. I no longer recommend the yellow probe in the picture below. They have not lasted. Instead, I recommend inexpensive pH probes from Hanna as its a trusted company that focuses on pH–and its really easy to calibrate. Click for their inexpensive model.

pH probes
Note the cloudy water. That’s dust from the gravel even though it was rinsed. This dust needs to settle for two days before we add a fish. The distilled water beaker is for rinsing probes.

I like the Milwaukee MW600 LED Economy Portable Dissolved Oxygen Meter, because they last a long time and rarely need calibration. Plus, they’re inexpensive on Amazon (under $200). I’ve heard good things about the optical dissolved oxygen probes from Vernier or Pasco too.

Dissolved oxygen probe and student taking data on their spreadsheet.

We take group nitrate and nitrite data since the water is all from the same source.  This saves money. After this day, the students will take their own readings using strips.  I use strips instead of probes, because nitrate probes are notoriously difficult and lose calibration easily–sometimes in the middle of a period and take 30 min to calibrate. Forget it! I learned a new trick last year–slice the strips in half vertically and they last twice as long! A HUGE money saver!
These strips have served me well for years Industrial Test Systems 480009 WaterWorks Nitrate/Nitrite Nitrogen

I use nitrate test strips as I don’t like nitrate probes. I buy several bottles each year for ecocolumns. This picture shows a full strip, but you can slice in half long-ways to make skinnier strips and stretch your money twice as long!

Below is a video on how to use each of the probes and strips.

After two more days, your students will LOVE your class, because they get a fish!

Adding Fish to Ecocolumns

Ecocolumn Fish–“O Happy Day!”

After weeks of your students being excited about getting a fish, today is the day!

Word of caution–don’t add a fish for two weeks after building the initial column and for two days after building the aquatic chamber.  Seriously–don’t do it. I did not heed the warnings myself the first time I built and had massive fish death.  Your students will keep bugging you about fish, but teach them patience. The reasons why are found in my previous post-Building the Aquatic Chamber.

Student directions for building ecocolumns.

Read about buying supplies, cutting and filling bottles, planting seeds and taking data , adding bugs, worms and leaf litter, and building the aquatic chamber in previous posts.

What Fish to Add?

Gambusia (mosquito fish) are my favorite and I keep them year-round in 3 ten-gallon aquariums, but minnows and guppies also work well. You can purchase Gambusia from Carolina Biological or ask your local health department vector control for some.

Let’s discuss some of the popular varieties of fish for ecocolumns. There are many bad choice and to be honest, I’ve used some or allowed students to buy and wish I knew this information. Shout out to Katy Sturges for some of the info on fish no-nos.

Goldfish: Cheap, but not good for ecocolumns. Their waste contains a large amount of ammonia which will burn their scales (black spots). They will also eat all of the elodea leaves quickly and kill it. You may need to replace the elodea or supplement with fish food.

Rosy Red Minnows: Feeder fish so they’re cheap like goldfish, but I’ve found that they have a high mortality rate. Since they’re so cheap, you can replace easily when they die (Dead fish teach a lot about nutrient cycling when students bury in their soil).  Will sometimes eat a lot of elodea too.

Beta (Chinese Fighting Fish): Some people use in ecocolumns, because they can gulp air from the surface and will survive when dissolved oxygen levels are low. The problem, however, is that they are insectivores and will only eat the elodea if desperate. They need a supply of brine shrimp, zooplankton, daphnia, or mosquito larvae. If you use healthy pond water with these invertebrates, this might do the trick.  The other problem is that they can see each other in adjacent ecocolumns which stresses them out. There are, however, creative ways to remedy the problems and use beta fish.

Guppies:  A good choice, but can be pricey if you have a lot of columns. They can tolerate cold and dirty water and aren’t too large to use up the dissolved oxygen. Some of my students purchase these at the pet store.

Gambusia (Mosquito Fish): My favorite. My original population came from Los Angeles County Vector Control which donated a bunch. Vector Control uses these fish in abandoned pools or ponds to eat mosquitos and their larvae (hence the name). Can also be purchased from Carolina Biological, but they have a hefty price if you include the shipping cost.  If you purchase some or get some donated, try to keep year-round. They will breed and keep your stock going. I have a super strong stock now as the weak ones have died off and the strong keep breeding. Natural selection at work! A draw-back to Gambusia is that they are omnivores and prefer to eat invertebrates. But, they will eat the elodea and survive in Ecocolumns for several weeks.

Tetra: I’ve heard good things about these fish from other teachers, but have never used myself. Can also tolerate cold, dirty water.

Snails: A good solution if you can’t find any healthy fish to add. Snails are often pests at the pet store and they will give them away to you. They will eat algae.

Take Water Quality Data First

Students should take water quality data first before adding a fish. They need to see what changed in their water after the elodea has been in the water for a couple of days. Students also should take other data–plant height, soil etc.

Dissolved oxygen probe and student taking data on their spreadsheet.

After taking water quality data, students can add a fish. Make sure the dissolved oxygen levels are higher than 3 mg/L before adding a fish. They should be if students cut some flap/air holes in the chamber.

Adding a Fish

Students getting a fish from my stock tanks.
Student who bought their own guppy from the pet store.

As a rule of thumb, students can add up to two small fish (guppy-sized) or one medium-sized fish (1-2 inches). If they add more, they run the risk of killing them all due to dissolved oxygen depletion.

This is the last stage of building the ecocolumn. I try to have students take data again within a few days to see nitrates building up in the water and then weekly after that.











Bugs, Worms, and Leaf Litter…..O my! (Adding detritivores to EcoColumns)

Adding worms is almost as much fun as getting a fish!  (NO FISH for two weeks–seriously, don’t do it)

After a week of letting the seeds germinate and grow, its time to add bugs.  Students will also measure their plant height, take soil data, and add to the spreadsheet on this day.

Student directions for building ecocolumns.

Read about buying supplies, cutting and filling bottles, planting seeds and taking data in previous posts. 

Adding Detritivores

Students should take terrestrial chamber data today-before or after adding detritivores: Plant heights and observations. Soil data also if you have probes or kits (optional).

We add detritivores (insects that decompose) which allows students to learn more about nutrient cycling. NO herbivores as they will eat all the seedlings and plants.  NO carnivores (spiders, lady bugs) as they won’t have any food and will crawl/fly away. NO crawling or flying insects as they will escape.  (Believe me, you don’t want crickets chirping in your building) Initially, my students think the sprinkler top will keep the crawling bugs in, but I tell them we discard/recycle the sprinkler top soon as they plants need more room to grow.

You can take the kids on a bug hunt around campus or have them collect and bring from home. I tell kids to bring from home–go in their yards or the park and turn over rocks to find bugs and worms.  I also tell them that if they’re SUPER WIMPY they can buy worms at Walmart (bait/fishing section) and mealworms at the pet store (not a worm, but beetle larvae).

The best detritivores are ones that are easily found are earthworms, pill-bugs/sowbugs/roly polys, pinscher bugs, and beetles. Be careful as some will find caterpillars which are super cool, but eat all the plants.

Worms and bugs that a student collected at home.
Purchased worms.
Directions for students.
Handling worms is new for some kids. “Nope, you don’t need gloves”.

Side note: There is a way to add a non-venemous spider to your ecocolumns. You can have students add a piece of fruit to a chamber in order to attract fruit flies. When the flies arrive, you now have a food source for spiders. I don’t do this, but have heard its possible.

Providing Leaf Litter

Bugs need hiding places and food and leaf litter provides all that. My students go outside and collect a few green and brown leaves. They tear up and line the soil with leaf litter. They must be careful to avoid smothering seedlings. Its been a week since seeds were planted so most have germinated and grown at this point.

Students continue to drain their chambers. The more silt that flushes through, the better it is for the fish. Fish are not added for 2 weeks.

My students live in the Chaparral (well, technically in the suburbs surrounded by Chaparral), so many have never heard of “leaf litter” or know its function. This is a great opportunity for them to learn that in addition to hiding places and food for the detritivores, leaf litter prevents water loss, prevents erosion, and add nutrients to the soil.

Students take notes to help them understand the scientific concepts in ecocolumns. They will use these notes and their data to help answer analytical questions later and to make connections.

From experience, I’ve found that students need help with the scientific concepts in ecocolumns. A lot of the concepts are inferred and cannot be directly observed (part of biogeochemical cycles, for example).  Just making observations and having them research what’s going doesn’t lead them to the immense amount they can potentially learn. Scaffolding is important. I give notes and then refer to these concepts all the time. Students then have to process their notes, data and observations in more higher-level ways. The AP® Exam contains 2/3 higher level thinking questions so these skills are important. 

To find time for these essential skills, I flipped my class last year and enjoy the time to build higher-level thinking in my students. Even with the time, after a few weeks of ecocolumns, I train my students to spend only 10 minutes taking data.

Students store in my hallway under plant lights. I’ve purchased several banks with grant money. Window also work.

In an additional week, its time to build the aquatic chamber and add a fish.


Planting Seeds in EcoColumns, Taking Soil Data and Setting Up Data Charts

On the second day of building ecocolumns, students add seeds and begin taking data.  (This can be the second hour of a block period). Before they do this, however, they need to make sure their chambers are draining properly.

Download student picture directions to build Ecocolumns.

Read about purchasing supplies and cutting and filling the bottles which are previous steps.

Students drain the terrestrial and filter chambers several times and clear out any clogs before planting seeds. See the student picture directions (link above) to learn how to unclog holes.

Planting Seeds

When the terrestrial chamber is draining properly, it is time to plant seeds. Its REALLY important to make sure they drain, drain, drain, several times as silt can clog up the drainage holes on the 5th draining or so.  If the drainage gets clogged after they plant seeds in the soil, the soil and seeds get moved around (erosion) and buried too deep.

Students can choose 5 different seeds to plant. I make them choose 2 legumes out of the 5 in order to learn about nitrogen fixation.

I like to give choices to kids as they take more ownership of the lab.
Students need a lot of instruction about planting seeds as many have never planted seeds since elementary school. Only 1 seed per hole and only 1 cm deep. Make them measure it as many don’t really know what 1 cm is.

Try to buy seeds that germinate quickly.  Students get very concerned when some of their seeds germinate and others take 2 weeks. They think there’s something wrong.  Although that too, is a good learning experience.

Students need to label with a sharpie on the side of the bottle where the seeds are planted. Mine number 1-4 for each corner and 5 for the middle. Five seeds is really too much for the amount of soil, but kids like choosing that many and will learn about limiting factors.
Students planting seeds.

I show my students about 2 minutes of this video below to show them how to write on the bottles and plant the seeds.

Setting up Data

Long-term data collection and analysis is an important way to build higher-level thinking skills. The majority of the AP® Exam consists of higher-level thinking questions and students need practice.

Students need to crate a data chart. Since we now have enough laptops, my students currently use Google Sheets and share with me so I can spot check/grade their data. For many years, my students took hand-written data.

I require my groups to rotate the duty of filling in the spreadsheet as we take weekly data. This makes sure all kids get practice using spreadsheets-an essential skill in many jobs.

TEACH them how to make a spreadsheet as most teens don’t know how. Scaffold, give templates, teach how to “wrap text”. Mine have always been very appreciative to learn this skill. Your template will include the specific tests that you have equipment for–probes, test strips, test kits, etc.  The spreadsheet template I use is found on the student directions. 

Students also need to be taught that when we don’t take data for a certain test, they should not enter “0” as this is a real quantity. They need to leave the box blank.

Soil Data

Soil data is not a necessity, but if you have some funds to buy some probes or soil test kits, it can be a good addition to ecocolumn data.  Last year, I purchased several of these probes so my students now add soil temperature, pH, and combined NPK fertility. Again, don’t worry if you don’t do soil tests, I didn’t for the first 10 years of ecocolumns. Collect equipment over time. The picture below is of a soil probe which I bought 10 years after starting ecocolumns.

Since my students now take soil data weekly, by the time we cover soil several chapters later, they have some familiarity with it and I can save time by not doing a chemistry of soil lab.

Rapidtest soil probe analyzer.
You can also use these tests. I used for many years-not for ecocolumns, but for a chemistry of soil lab. Some teachers, however, use for ecocolumns several times during the lab.

After planting seeds, students should only water using the “sprinkler” they made when they were cutting bottles.  This will gently water the soil without causing erosion and displacement of seeds.

This is the “sprinkler” top that has holes burned in it. It goes on the very top of the column.

Let your plants grow for about a week.  DON’T MAKE YOUR AQUATIC CHAMBER AND ADD FISH YET.

After a week, you can add bugs, worms and leaf litter. 



Cutting and Filling Ecocolumns

Students thoroughly enjoy building ecocolumns. Building usually takes 2 full class periods (50-55 min). The example here is of an an ecocolumn with three chambers, a terrestrial chamber on the top with soil, plants and invertebrates, a filter chamber with sand and gravel, and an aquatic chamber with fish and water plants. For supplies needed, read the previous post.

Cutting the bottles

This is a “how-to” video explaining how to cut the bottles and create drainage holes in the lids.

I give my students a set of picture instructions. These instructions can be downloaded for free on Teachers Pay Teachers.

Cutting and filling usually takes the first day.

Bottles should be cut into these shapes. Maximize length on each bottle
Cut air holes in this bottle.
Use a tea light candle to heat up a dissection probe and burn holes in the caps
Its VERY important that one cap have 1mm holes and the other have 3 mm holes.
Measure the holes to make sure they are at 3 mm for the terrestrial chamber drainage. If they are not, it may clog.
Another option is for the teacher to us a bunsen burner to heat the probe and make one large hole for yarn. (Courtesy of Laura Solarez)
The yarn flows from the terrestrial chamber to the filter chamber with no knots (courtesy of Laura Solarez)
Burn holes in one of the cut off pieces to create a “sprinkler” to gently water seeds


Cutting bottles. Teach students to cut away from the body.
Trimming bottles using scissors so bottles nestle together well.
Burning holes in drainage caps
Measuring to make air flow “flaps” or “holes”

Filling the Bottles

This video shows you how to fill the ecocolumn chambers:

Below are some pictures of how to fill the chambers. Please DO NOT make an aquatic chamber at this time. Many dead fish have resulted from making the aquatic chamber too soon. You must wait 2 weeks.

Add gravel at the bottom of the terrestrial chamber and the filter chamber and then potting soil about halfway up the terrestrial chamber. Add 7-8 cm of sand on top of the gravel in the filter chamber. Let both chambers drain many many times. The sand will drain more slowly than the soil.
Filling a colander with gravel to take to the sink and wash thoroughly
Washing the gravel
Filling a chamber with gravel and then potting soil

At this point, students can clean up or if in a block period, they can go onto draining, planting seeds, setting up data, and taking soil data.