Lately I have developed an interest in aquaponics; the art and science of growing vegetables in a hydroponic system using fish waste (poop and dirty water) as the fertiliser and growing fish in an aquaculture system using plants to clean the water (hence the name). For years I have been against hydroponic growing; I have always believed that the plants do not contain all of the micro-nutrients we need as they rely on a chemical mix for food and it is wasteful when it comes to water. The idea of using the water fish live in to feed plants really made sense to me when I read about it; the fish poop has many living bacteria and lots of micro-nutrients (depending on what the fish are eating of course) and the nitrite (from ammonia produced by the fish) is converted to nitrates by bacteria in the system. The nitrates are then used by the plants to grow.
It seems to me that this is close to the natural system; fish living in a farm dam rely on the plant life in the same dam to clean the water for them and the plants love the nitrates the fish provide…isn’t nature amazing?
I have done a fair bit of research and reading about setting up a system;
Set up a cheap aquaponics system at home- https://www.urbanorganicyield.com/build-simple-aquaponics-system/
A general overview of aquaponics and specific advice. This guy has an entire series- https://www.youtube.com/watch?v=qXtvljDYkfI&t=757s
Nitrogen in aquaponics systems- https://university.upstartfarmers.com/blog/nitrogen-in-aquaponics
To build a simple seat-of-the-pants system you need; a tub to hold fish (big enough to house the fish you plan to put in it), a tub to grow plants in soil-less media (at least 30cm deep) and a way to move water from the fish tank to the grow tub and back again. The two kinds of bacteria needed to make the system work will apparently colonize on their own if the system is operated for a month or so with no fish in it (I will have to put fish food in though, to attract the bacteria).
After looking at some kits for complete set ups at home, I decided to try a cheaper (much cheaper) small system first to see if I liked it.
A trip to town yielded two tubs, and an online shopping session yielded a bag of growing media (clay balls) and a small, cheap solar pump.
An hour or so of fussing around and I have a small aquaponics system. Now all I need are some fish.
Recently we have been baby sitting some fish for a friend who is moving house and among her collection is a fish affectionately known as A*****e, because he attacks any other fish he lives with. While we have had him here, he has eaten the tail of a silver dollar and killed a crayfish. We put him in an outside tank for the moment, but I will move him to the aquaculture system when it has gone through the start up cycle.
The start up cycle. as I understand it, is a series of biological cycles which make the water livable for fish. First I add fish food which produces ammonia as it rots, this attracts the bacteria that converts the ammonia (toxic to fish) to nitrites (still toxic to fish) which attracts the bacteria that converts nitrites to nitrates (not toxic to fish and available to plants for nutrient). This takes between two and six weeks.
I have added plants (in the form of lettuce and spinach) to the system and have also added water from the indoor fish tanks to provide some nutrient to my baby lettuce while they wait for the cycle to complete. I will post an update when I add the fish to the system.