After struggling for a long time with how to keep my fish tank as clean as possible (with as little effort as possible) and failing miserably I finally discovered aquaponics – and I wanted it. This system is so special it covers looking after fish, upcycling materials and growing your own food! The problem was most aquaponics systems costs hundreds of pounds and I had about a tenner to spare, if that.
I was not to be deterred however, I wanted one, so I was going to figure out how to build my own. I already had a small fish tank with a terrible water filter that dribbled out water at best and needed changing every week. I wanted to convert this into a self cleaning system that also provided food.
How Aquaponics Works
Aquaponics is amazingly simple really. All you need is a pump to pump the water from the fish tank to a tray with various sized filtering rocks in it. Here you plant a bunch of cress seeds (or even lettuce) on top of the rocks. The idea is the plants use the fish poo and turn it into nutrients to grow. Then, the water needs to be directed back down either into a second tray or into the fish tank again. The falling water being a bit cleaner than before and oxidizing the tank.
Cost to DO:
If you already have fish and a fish pump: £0
If you do not have a pump : £10 +costs of tank and fish according to your requirements.
Our zebra fish are around £7 each, snails to eat algae are 75p each (because our zebra fish are in cold water) and the tank was free from friends (you can also scour freecycle and supermarket adverts). While we did also get a free pump it broke within a few days and we had to purchase a new one – we got the cheapest one around which was £10 from our local pet store. Since we are improving the flow capability of this pump anyway a cheap one will be sufficient.
- Glue/Glue Gun/Super Glue
- Plastic tray – such as those from supermarket bread/pastry products
- Plastic tubes (we used kids toy tubes from a pirate bed – they were the perfect fit for the pump attachment!)
- Gravel of different sizes (taken from the original filter and replacement filters and the fish tank gravel)
- A couple of small bottles (those little innocent smoothie bottles work great)
- A water pump (taken from the original filter). You can purchase a pump on its own but it’s actually cheaper to just buy the cheapest tank filter instead and get the extra gravel this way as a bonus.
First of all before we begin, I would like to let you know that the aquaponics system isn’t the one I first built. The one I will be teaching you to make today is our Aquaponics Mark II system.
The first one looked like this:
There were however several problems with this design that only emerged afterwards including:
- Not enough space for cress – it grows hard and fast and we want more!
- Roots clogged up holes
- Holes were leaky
- Fish filter pump was not enclosed enough
So we decided to create Aquaponics Mark II and significantly improved upon it’s design with some rather intuitive solutions if I do say so myself.
Gather together your materials including plastic tray (I prefer see through to maximise light access), plastic tubing, scissors, and glue (i used a glue gun before but ran out of sticks so used super glue this time).
Cut the tube into two sections: 1 long one to fit from the pump to the fish tank lid, and one short one to fit from the fish tank lid to just above the water level of the tank. The long tube will be your water out section and the short one will direct the water back in.
Line up the plastic tray against your fish tank lid. Later on it will be glued into place but not now (just in case something goes wrong). Mark out where you want your tubes to go so that they go through the existing holes in the fish tank lid. I placed my output tube on the right hand side (so that the pump will be at the side of the tank and the power cable is closest to the wall socket). The shorter input tube I placed at the back middle of the lid/tray.
Put a hole through the marks and ease the tubes in, glue in place inside the plastic tray so that water can’t leak out (you can use bath sealant I guess if you have some spare). Allow to dry thoroughly before exposing to water.
Take your small plastic bottle and check the water pump you have will fit inside it. The pump should be easy to remove from the fish filter and won’t require any tomfoolery. For my filter I found it fit easily with plenty of room into an innocent smoothie bottle.
Get your knife/scissors and score thin line holes at 90 degree points at the base of the bottle like in the picture above. You don’t need to widen these holes this will be plenty for the water to get into without endangering small fish.
Remove the lid of the bottle and make a hole in the middle. Thread the long tube attached to the tray through this hole. Do not glue it in place (we want to minimise the use of glue where possible both for the fish and for the sake of easy removal and replacement of parts).
Cut the Bottle in half above the pump and slot the pump inside. There should be plenty of breathing room in there.
Cut a line hole in the top of the bottle and thread the wire through it (since it is attached to a pump at one end and a plug at the other, you need to cut a line to thread it through not just a hole for the wire). Do not seal the top of the bottle into the base yet – attach the long output tube to the pump first threaded through the open bottle top. Then screw the bottle top to the lid on the tube and finally slot the top half of the bottle inside the bottom half of the bottle so that the pump is covered and cannot trap fish.
Secure the plastic tray to the fish tank lid with glue in the corners. If using super glue you will need to sit around for a long time. A glue gun is much faster to dry. When it is dry, place the system into the fish tank and close the lid in place. Check that the short tube is suspended inside the fish tank above the water level and that the pump bottle fills with water and is weighed down sufficiently.
Now is the time to check your system works before progressing further. It should all work fine but if your holes are too small, or too big you may have water flow problems or leaks and now is the time to fix those before finishing the system. Thankfully ours did not have leaks and had excellent water flow, yay! Remember we had a piddly slow water pump? Not anymore! Thanks to the vastly superior filter system the water flow was much better, some pre-built fish water filters are just designed very badly. Time to move on…
In this design we also created a removable tube protection system that acted as an additional filter. This device will use the bio sponge found in your old fish filter providing a third method of cleaning the water. This sponge needs regular cleaning, so its important it’s not fixed into place – which means a tricky problem to solve for our aquaponics system. We found in our Aquaponics Mark I system, placing the sponge into the tube meant daily cleaning required and a vastly reduced water flow so this time we went for something a bit more daring.
Take your second small bottle and cut the top off. Then cut a small rectangle (smaller than the bio sponge you have) into the bottom side of the bottle.
Then with the bottom half of the bottle cut a thin strip off the top so it makes a circle like this.
Slot the strip of plastic into the base of the top half of the bottle so that it covers the rectangular hole you created. You should find the plastic bends inwards a bit creating a gap as the plastic ring is slightly bigger than the bottle top half. This is great and just what we need to get water through the sponge so align this inward bend so that it is behind the rectangular hole you created.
Then place the sponge between the plastic like above. It will be clamped in to place by the plastic strip but still allow water to pass through the sponge. Your tube protection device can now be sat on the plastic tray around the shorter tube hole. This will help stop roots clogging up the tube and provide an extra filter for the water exiting the system. Not all of the water will go through the sponge but it will capture a lot. It does not need anything to weigh it down – it will be heavy enough and the water flow won’t disturb it.
When the sponge gets brown – rinse it under a tap and then replace it. Turn the bottle top periodically to sever ambitious roots heading for your tube hole.
Fill the tray with your smallest gravel from the filter, then the second smallest, then the biggest and finally with the gravel from the bottom of your fish tank (after you have cleaned it all). This creates several layers of filtration. Make sure the level of the gravel is higher than the stable water level when the pump is on to help prevent seed movement.
Finally, scatter some cress seeds on the gravel, put your fish tank by a window and turn on the pump. Check the water flow is still good to ensure sufficient oxidisation of the water for the fish. Wait 3-6 days and eat the resulting cress – plant more on top and repeat the process!
If you do not have a spare window you can get a special growing LED bulb plate to fix above your fish tank but this will cost around £20.
Congratulations, you are finished!
Great job on getting this far, you now have your own aquaponics system that will/is:
- Oxidise your water
- Provide a multi-filtration system by: Plants, Gravel layers and Bio Sponge
- Provide quick and easy to grow healthy food to snack on and use in salads (the kids will LOVE this!)
- Make happier healthier fish
- Reduced cleaning for your fish tank required (deep clean once a month if the water starts going green and consider adding one or two water snails).
- An amazing self sufficient system you didn’t pay £400 for.
In a few days your tray will look something like this one did (picture from Aquaponics Mark I):