After getting the aquaponics system all set up in the basement, I had no appetite for spending any more money on this project. One thing I did buy, and I’m very glad I did, is a digital scale. If you are doing aquaponics or thinking of it, I recommend you do, too. My scale was only 15 bucks, but it does everything I need: it holds up to five kilograms, it has one gram accuracy, and it has a tare function, meaning you can zero the weight of the container.
The thing that prompted me to buy the scale, was the issue of how much to feed my fish. I don’t have very many fish, and I want to maximize their ammonia outputs without over feeding them. Young fish can be fed 2 – 3% of their body weight per day, but I had no idea how much that was. So I weighed my fish. It turns out that my fish were about 12 grams each, times 8 equals 96 grams of fish. So I can feed them 2 – 3 grams of dry food per day. My next problem was that I feed a frozen gel food in addition to pellets, and I needed to find out what percentage of the gel, by weight, is food and what is water. I weighed out some gel food and microwaved it until it was hard, then weighed it again. It turns out to be about 20% dry food, so now I can figure out how much to feed. I usually feed about 8 grams of gel and 1 gram of pellets per day, about 2.5 grams of dry food equivalent.
In another post, I mentioned that I add iron to the water to prevent iron deficiency in the plants. The recommended rate is 2 mg of pure iron per litre of system water, every 3 weeks, which in my system comes to 14 grams of 7% chelated iron. I don’t know about you, but I’m not very good at eyeballing powdered iron, and the scale takes all the guesswork out of it.
I’ve also been weighing my harvests. I keep a system journal with all the water parameters and everything I do or add to the system. Knowing how much is coming out of the system is just as important as knowing how much went in.
So if you are making a list of required equipment for your aquaponic project, don’t forget the digital scale!