A few years ago I had a small aquarium that had no filter and was cleaned using aquaponics. It was a tiny system with Endler's livebearers, and it worked incredibly well.
I recently tried a tinier aquaponics in a jar, which failed miserably. I have a few ideas which could possibly make it successful. I need to write a post on that.
I would love to try a larger aquaponics system with edible fish some day, but fish food is so expensive that I just can't see how it could ever be financially viable. So for now I will focus on ornamental fish which I already have and am already buying food for them, rather than trying to grow and harvest edible fish.
I currently have a barrel full of goldfish. I have only had them for a few months, but so far they are growing well and looking healthy. I decided to make my barrel into a little barrel aquaponics system.
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Various herbs in a floating pot, growing well
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Winter is coming, and I know some plants will only grow well over summer while others will do better over winter. I only have room for one little floating pot at the moment so I decided to plant a mix of herbs and other edible things.
I planted silverbeet, Vietnamese coriander, water celery, spearmint, and have recently added native river mint.
The native river mint has not been in long enough for me to comment on its growth. It is growing larger and I have high hopes for it to perform well in here.
I had expected the silverbeet to perform the best out of all these plants in the cooler weather. So far it has performed poorly, it is alive but not really growing and certainly not thriving. I am not sure what the problem is, maybe it needs a larger pot volume for the roots, or maybe it just needs more time. I don't think its roots have grown into the water yet.
Spear mint is a garden thug and loves damp places, so should perform well. So far it has not fared too well, I think this is due to the cooler weather. It is growing slowly, and is dropping leaves. Mint tends to go partly dormant over winter here, so I am not expecting to see a lot of growth from it until things warm up a little.
Water celery has done well, it survives pretty much anything. Hot, cold, wet, dry, blasting sun, part shade, it always survives. I had a feeling it would do well in a floating pot, and it has. Over winter it usually does not grow a lot. It gets nice colours when the temperature drops. So far it has done well and is getting larger.
The real stand out so far is the Vietnamese coriander. This herb generally does not like cooler weather, but has grown like crazy since I put an unrooted cutting in this floating pot. I suspect most of the roots in the water are from this plant. Perhaps over winter it will die back somewhat, or maybe it will be protected enough to keep growing, time will tell. I am confident it will survive and be one of the first to spring into growth when spring hits. If it grows this well over autumn I can hardly wait to see what it can do over spring and summer!
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The roots are growing longer, maybe I won't need a spawning mop in spring
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Initially the fish were eating the plant roots as soon as they protruded from the pot. Now the roots are growing faster than they are being eaten. This is good as it means the plants have more access to nitrates etc in the water. I took the above photo a week or two ago, the roots are probably triple that length now, which is a good sign.
I had planned on putting a spawning mop in the barrel in spring, if the roots grow long enough this may not be needed. Time will tell, perhaps once the fish are larger and the weather is warmer they may devour the roots.
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Very simple set up
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The barrel only has a small air water interface, it is deep and holds a lot of water, and very little of the water is exposed to the air for gas exchange.
I have a pot of plants floating on the surface which is reducing the surface area. I also tend to have some azolla and duckweed on the surface, this is eaten by the fish but while it lasts it reduces the surface area even more.
The fish are all using oxygen from the water, as are the plant roots, this combined with such a small surface area could be problematic. I could try to grow some oxygenator plants in the water, but the goldfish eat them out too fast for them to make any noticeable difference to dissolved oxygen levels.
Goldfish are pretty hardy, and can gulp air if needed, but I like my fish. If I don't want to be cruel to my little fish I needed to put in a pump to oxygenate the water.
I have a small solar pump which brings water from the bottom of the
barrel to the surface where is gets oxygenated. I was originally pumping it
straight back into the barrel. This was not oxygenating as well as I had
hoped as it was just a continuous stream of water. It was increasing the surface area and circulating the water, which is fine in cooler weather, but it needed something better if it is to work well on warmer days.
I then tried pumping the water through a small pot full of gravel, which was working much
better. This pot of gravel breaks up the stream of water and makes it splash and bubble into the barrel. Much more oxygen plus the fish seem to enjoy swimming through the stream of splashing water.
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| water pumped through a tiny pot of gravel |
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azolla and duckweed are eaten by the fish
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The little pot of gravel did a great job at breaking the flow of water, but did little for housing the nitrifying bacteria and improving water quality. Now I have a milk bottle of gravel that I pump the water through.
The milk bottle provides more gravel and housing sites for the good bacteria, and should slightly lower nitrates in the water column. The water splashes out of the milk bottle and oxygenates the barrel water. I haven't planted anything in it yet but it is large enough that I will be able to grow a few plants in there.
I have some wire on top of the barrel to prevent birds from stealing the fish. At the moment I sit the milk bottle on top of that. It is easy enough to lift this off whenever I want to feed the fish or whatever. The fish are really interactive, so it is nice to lift off the wire and be able to see them better.
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| Milk bottle of gravel to be used as a small grow bed |
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The barrel full of fish
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I know what you are thinking, and you are correct. That tiny pot of herbs along with a milk bottle of gravel is not enough to clean an entire barrel's worth of water.
At the moment the weather is cooling and the fish are not eating much, they not producing much waste, so the small floating pot of herbs along with the azolla and duckweed is going ok. I am also doing small water changes each week, and putting the nutrient rich water on fruit trees and on the vegetable garden. At this point in time this is keeping the nitrates low enough.
Hopefully my little fish all survive the winter. Once the weather warms the fish will eat more, and grow more, and they will produce significantly more waste.
I have plans for a small flood and drain grow bed to put on top of the barrel. I plan to pump the water through the grow bed instead of the milk bottle of gravel. I would love to grow some nutrient hungry vegetables up there including tomatoes and kangkong (I love kangkong). I don't want to do that until after winter has ended.
