Ever wondered what to do with that old fish tank in your classroom? Lots of teachers have classroom fish but are not really using them as a teaching tool. Why not transform them into a self-sufficient system to help show students the Nitrogen Cycle (and other things) in action? It’s easy and the possibilities for use in classroom instruction are endless……
Start with a fish tank (mine is 10 gallons) *cat not included* 😛
Then you’ll need some things you can pick up at Lowe’s, Home Depot, or any hardware store:
- Vinyl Gutter (about $4 for a 10 ft piece)
- Gutter End Caps (you’ll need 4~ about $3 each)
- Gutter Brackets (you’ll need 2~ about $3 each)
- Clear Silicone Caulk (exterior, waterproof~This is the only kind that’s safe for fish~ about $5)
- Clear PVC vinyl tubing (I used 5/8th inch tubing~ about $6 for 25 ft)
- “T” Connector for tubing (It’s actually called a “nylon hose barb” It fits inside the nylon tubing~ I used 1/2 inch inner diameter one)
- Foam Board Insulation (I used 1 inch thick, comes in 8 ft sheet~ about $15)
- Pea Gravel (you’ll need 1 bag~ I used the large size~ about $4 per bag)
- Small Submersible Fountain Pump (about $20)
Tools you might need:
- Scissors (for cutting the tubing)
- Utility knife (for the foam board)
- Hacksaw (or something similar) to cut the vinyl gutter
- Tape Measure
Let’s Get Started!
1. Set up your fish tank and pump. Mine is an under gravel filter that I built last week in a workshop but I imagine that any standard filter will work. If you look around the cat head, you can see mine 🙂 I also used the same pea gravel on the bottom of my tank that I used in my gutters (WASH it before you put it in the tank or you’ll have a mess).
2. Measure and cut your foam board. I made mine slightly larger than the tank to support the gutters. Foam board is really easy to cut.. Just score it with a utility knife, then pop it over your knee and it splits cleanly.
Here’s the foam board I used:
3. Cut out the center of the foam board 3 inches from the edge. It will be in a rectangle. This allows a place for the water to flow back into the tank from the plants. Also, notch out places for the air supply lines or any cords.
Once you put the fountain pump in and connect the pipe to the plants, you will need to make another notch to hold the pipe.
4. Measure and cut the gutters. Important note: Make sure to cut the ends straight or the end caps won’t fit well and your system will leak! Ask me how I know…… 🙂 Make sure to cut them longer than the tank so they will fit on the foam board you already cut. I think mine are 24 inches long.
Put the end caps on the gutters and mark your drill holes. I drilled them 4 inches apart, and under the “bend” of the gutter. I figured out it was better to have them a little low than a little high on the side of the gutter. I also drilled 3 on 1 gutter and 4 on the other so they would alternate and the water would flow back in the tank efficiently. Make sure you clean out the holes because the vinyl doesn’t always drill cleanly. Add the end caps (They don’t snap over the gutter, they simply butt up next to the gutter~ This took me a few minutes to figure out lol). Use silicone caulk on both the inside and the outside of your seal. (Yes, it stinks 😛 ) Make sure to cover the seal completely, use your finger to smooth it out. Set it aside and let it dry and cure. I waited overnight before I put any water in it. Next morning, fill with water and check for leaks. Recaulk as needed. Let dry completely.
This is video of the water flow pattern into the tank. Notice how the water streams alternate. This cuts down on splashing… and the fish just LOVE to get under them 🙂
5. Assembling the tubing. First, check your fountain pump and make sure the tubing fits over the large adapter. Don’t use the aquarium tubing because it is way too small in diameter to get adequate water flow to your plants.
(This is my little fountain pump even though the picture is a little fuzzy 😦 )
I used 5/8th inch tubing I found in the plumbing section. You will also need a “T” connector (actually called a “nylon hose barb”). The one that is 1/2 inch inner diameter will work with the 5/8 inch tubing.
Put the foam board on top of the tank and the gutter on the foam board. I went ahead and snapped the gutters into the gutter brackets just to make sure I got the tubing long enough.
Put your fountain in the tank (mine had little suction cup feet so I stuck it to the back glass. Measure the depth of your tank from the bottom where your filter is to the top edge of your gutter. I added a couple of inches to the measurement just in case (Btw, the tubing is easy to cut with scissors). Then, I measured the inner length of the gutter and cut 2 pieces this length. The tubing needs to fit inside the gutter at all times or you’ll pump the water directly out of the tank onto the floor… Ask me how I know 🙂
Attach the tubing to the “T” connector, then to the fountain pump. Test the flow level (and for leaks in your gutter). If it is too strong, you can adjust the rate of flow on the fountain pump (mine is a little turn switch). You can also make sure the holes in the sides of the gutter are cleaned out and large enough. (I had to scrape mine out a little)
(I apparently have not mastered the art of caulking. This looks awful lol)
Make sure you position the gutter brackets so that the lowest edge is towards the inside of the tank so the water will flow in the right direction.
See how they tilt inwards towards each other?
6. Gravel. WASH the gravel before you put it in your gutters! (There is a ton of sand and dirt on it and you don’t want it in your tank). Fill your gutters with gravel but don’t just pack it in because it won’t drain well and will overflow (Ask me how I know 😛 ) I used the large size pea gravel.
Once you have gotten the flow rate adjusted, it is time to add the plants. Just make sure the water drains from all the holes you drilled and doesn’t back up into the gutters and overflow.
7. Time for plants. I didn’t get any special plants, just got normal herbs from the nursery (like the kind I would plant in the dirt).
I picked off as much of the little planting pot as I could.
Until I got to the dirt..
Then I took the hose and just washed until I got to the bare roots..
(Yes, I know, this is a basil plant and not rosemary.. but you get the idea 😛 )
My naked plant 🙂
The basil plant really had 3 plants in the pot. I separated them. I cut the roots lengthwise instead of chopping them off. Who knows if I’ve killed it at this point? Maybe it will make it 🙂
Then, I put each plant in a little net cup and “planted” it in my gutters filled with rocks.
I piled the rocks around each one and kind of on top of the plant just to keep them in place. Be careful not to obstruct the drainage holes… or the water will back up in the gutters and spill onto the floor…. (You know the story by now 🙂 )
I don’t know where you buy the little net cups. These were given to me at a workshop. I was thinking that when I need more, I might be able to use recycled K-cups (with holes punched in them).
So How Can I Use This With My Students?
This system is the Nitrogen Cycle in action. Fish poop–> Then the water takes the waste to the plants –> The plants use the nitrogen in the waste as fertilizer. It’s a win-win situation 🙂 I can think of a lot of ways to explore this with students… in addition to working on their critical thinking skills (analyzing the water, tracking the pH of the tank, graphing plant growth, not to mention plant and fish biology). They could even build their own system as a class. Think of the possibilities for problem-solving, measuring, cooperation, etc. I think it would make a wonderful vehicle for problem-based learning!
Many schools offer aquaponics (growing plants in conjunction with fish) as well as hydroponics (growing plants with just water, no fish). It is an exciting field of study that is rapidly gaining popularity with the rise in major scientific laboratories using Zebrafish to study disease instead of lab rats. I think this has a valuable place in any science classroom K-12. I can’t wait to see the results of my little herb garden. In fact, I am planning a larger scale project that incorporates my existing koi pond. I’m dangerous now that I know how to operate power tools 🙂