Wednesday, 14 May 2014

Small scale home aquaponics

My fish tank started to get a bit stinky and I don't have a lot of water here so am hesitant to do a water change.  Being outside it gets a few hours sun in the early morning so the sides get covered in algae.  I used to scrape it off on the viewing side from time to time.  I used to leave it on the other three sides so that it helped suck some of the nutrients out of the tank.  I also always try to have duckweed growing on top to help improve water quality.  This works fine as long as some of the water is changed very now and again.

Then I considered turning my fish tank into a mini aquaponics type tank.  I have been interested in aquaponics for some time now.  After a lot of tyre kicking I am ready to give it a go, but we are planning on moving soon so I do not want to start anything too big so this works out well and helped me to learn how to do it properly on a larger scale.

I had a little bit of styrofoam in the yard.  That got me thinking.  I wanted to set up something that would work with my fish tank, something that was simple, something cheap, and hopefully something productive.  The more simple the better.

I bought two tiny bristlenose fish (Ancistrus sp, or as my kids call them "nibble fish") to eat some of the algae, but then I still had a lot of ammonia, nitrites and nitrates to deal with.  Adding extra fish only makes this problem worse.  Duckweed helps, but there are a lot of fish in my tank producing a lot of waste.

I then got a piece of styrofoam, punched a few holes in it, and inserted some herb cuttings which had tiny roots.  Within two weeks the cuttings had long roots, the water no longer smelled bad, the sides had noticeably less algae on them, and the water was a lot clearer.  I had no idea that it was not all that clear before, but the difference is remarkable.  This was fantastic, but I am not sure if this is due to the plants or the new 'nibble fish' or a combination of both, chances are this will only work short term as the plants may rot with the roots being in water all the time and oxygen levels not being high enough.

I then set up a small fish tank at work with a pair of Endler's who began to breed.  I planned on using this to do small scale aquaponics and try to be as productive as possible.  After the fish had been in for a few weeks and increased in number somewhat I removed the filter and started the small scale aquaponics set up with an eye to work out potential problems and see how productive a tiny tank could be.  This tank is far smaller than my tank at home, but this tank has a light on it.

Many aquaponic gardeners start with deep water culture to keep things simple.  The Aztec floating rafts, or "chinampas" was a way to farm using deep water culture on a large scale.  Clearly this approach can and does work, but there are a few things that one has to do right to make it work well and I needed to teach myself what these things were.

The timeline for my tank at work is as follows:
25/03/2014 - the cuttings were set up
28/03/2014 - first set of photos
10/04/2014 - 2nd set of photos
29/04/2014 - 3rd set of photos
12/05/2014 - plants grew far too large and were harvested

First I got some styrofoam, punched a few holes in it and inserted some herb cuttings, just like the tank at home.  I increased the oxygen levels in the tank to help prevent them rotting.  As expected, these grew like crazy.  I then included a pot of gravel with another cutting.  I "seeded" this pot with beneficial bacteria to break down ammonia and nitrites faster.  The herb in this pot also grew like crazy so a few days later I included a second gravel filled pot with a different type of herb.

small scale aquaponics, the fish are in there somewhere too
aquaponics 3 days in

herb cuttings 3 days after planting - note the tiny roots
I had great plans of taking pictures each 2 weeks to show the growth and development of the plants.  I originally planted basil, mint and pineapple sage.

aquaponisc 2 weeks on

root and leaf growth after 2 weeks

plants larger after 2 weeks

2 weeks of growth, all looks good

Then I went on holiday for 2 weeks, upon my return the plants were huge and crowded under the light.  The roots are spread nicely throughout the water giving the fry a place to hide.  I held off doing anything for a while but the plants got too large, so I cut them back pretty hard.  We made mint and basil lemonade with the herbs.

small scale aquaponics
5 weeks of growth, ready for harvest

Classroom aquaponics
The herbs were larger than they look
I have learned a lot from doing this, many things I thought would happen have happened.  It is reassuring to see things growing in ways that I thought they logically should.  It is also nice to be able to work out any problems on a small scale before doing this on a larger scale with edible fish.  Regardless, I now know how to make this work for me simply and cheaply.

I also have started to grow some watercress in one of the pots, hopefully it does well in a floating pot but it is too early to tell yet.  I also have some seeds of kang kong which have just started to germinate, but I think it is a bit cold for them at the moment.


  1. That's really cool! I've wanted to do aquaponics using fish not for eating (we don't eat fish) but it's too hard when you're not in your own house. I love this idea, could possibly talk Eddie into this. :-)

  2. Melinda it sure is cheap/simple and short term it is giving amazing yields! The same herbs growing in soil outside are not currently giving any yield and are pretty much waiting for frost to knock them down. Perhaps this can be used to grow basil and other summer herbs over winter. I don't know how well it will go long term, but I have very little to lose by trying. I will let you know how this goes on a longer time frame.

    The floating pots of gravel seem to work much better than just floating a cutting in some styrofoam. The floating cuttings seem to work well for some plants but not others. The biggest things are ensuring that the dissolved oxygen levels are high and that the plants get enough light, other than that it runs itself. I am planning on trying some other herbs and some vegetables and see how they go.

  3. After 43 weeks of running this tiny system I sent home the fish and emptied the tank for the holidays as I did not want to drive to work to check on the fish. The only real problem I had was the lack of light.

    During those 43 weeks I never once changed the water or had a filter of any sort other than the plants. The fish gave birth every 3 to 4 weeks for the entire duration and each batch had substantially more fry so I assume they were reasonably happy. Other than feed the fish, harvest the herbs when I felt the urge and top up the water from time to time I did not do anything. I wanted to see if this could run on its own and it pretty much did.

    Some important points: you need an aerator or the dissolved oxygen will drop too low for the plant roots as well as the fish. The floating styrofoam is not as good as the floating pots but it does get cuttings to take very fast. Over winter the herbs did not do great, they survived but grew so slowly I began to worry about the water quality, lettuce or some sort of brassica would be far better to grow over this time. Solid waste sediment (ie fish poo) builds up on the bottom of the tank, it got kind of thick after 43 weeks, this is not a problem unless you want the tank to look nice. It would not be difficult to siphon this out once or twice a year and put it to good use somewhere.

    All in all I consider this a win, it was successful in growing herbs and keeping the fish healthy but more importantly I learned a lot from doing this. I would love to ramp this up a bit and grow some larger (possibly edible) fish and some larger vegetables but may not get around to it for a while. I also have plans for an even smaller system to put on my desk at work.