Backyard Aquaponics
A place to discuss aquaponics

Hi all,

I am a new member, but have been lurking and learning from you all for a couple of years. Last summer I started a small 30 gal water garden with three goldfish, to see if I could keep everything alive, and practice managing water quality. It has a pump to an urn containing bags of expanded clay, and the water flows back into the tub. I rinse the bags out every few months. I tried floating lettuce in the tank and, as expected, the goldfish ate the roots. The plants in it now are all in pots, and purely decorative. It consistently has a pH of 8, zero ammonia and nitrite, and nitrate of five ppm. I add a pinch of cheated iron Aquairon and a half teaspoon of powdered Maxicrop every two or three months, depending on the growing season.

In January I bought a used IBC and twelve half grown goldfish (I know, wimpy not to grow fish for food, but I don’t want to kill them.) and started a chop and flip system. It holds about 200 gallons and the media is expanded clay pebbles. The pump is on a timer, 15 min on, and 45 min off. It grew lettuce and carrots until the weather warmed up, then grew beets, cucumbers, strawberries, kale, and more lettuce until it got hot. Now it’s growing tomatoes, peppers, and one melon that only wants to produce male flowers. I also use the fish water for a strawberry tower and a couple of wicking pots. The parameters are running pH 6.5, ammonia and nitrite zero, and nitrate 5 ppm. I add Aquairon and Maxicrop to this system as well, and they have resolved the plant deficiencies I saw upon start up. My only disappointment has been the tomatoes, and I will probably confine them to wicking pots next year. I’m actually surprised that anything is surviving our summer heat right now, but the system does get some filtered afternoon shade. I wiped off a few aphids in the spring, and have been removing leaves infected with leaf miners and, recently, powdery mildew.

I have some questions. First, should I try to boost the nitrate by feeding more? I feed about five grams twice per day to the 12 goldfish, which are about five inches long. I don’t want to kill the fish by over feeding, just to get more veggies. Second, those of you in hot climates, what have you had the best success with, and do you ever empty out your grow bed and just maintain the fish until the weather cools down a bit? Lastly, how much aeration is enough? I’ve never seen any gasping fish, but worry about oxygenation as the water temp approaches 90 F.

5ppm nitrate is enough. Basically if the plants needed the nitrate you'd have a reading of zero. You may find that the reading drops to zero as the plants grow a bit more. If you decide to feed more be very careful - Your high pH and the high temp make an ammonia spike a definite possibility.

Re the tomato; Watch the roots to be sure they don't block the grow bed drain - tomatoes are notorious for doing this (confining them is a good idea). Mine don't usually produce till later in the season probably because the AP system takes longer to warm up enough - tomatoes like heat, although it sometimes causes problems with their flowers and pollination.

I'm not positive but I think your goldfish will be OK even with low oxygen levels in the tank, they are very tough fish.

Thank you for the information. I won’t change anything right now, until the temps drop a bit, and I’ll check my drain for roots.

Add rain water,distilled or de-ionised water to bring the PH down.But once that starts,it'll be a full time job keeping it up.

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Thank you , will do. We’ve been blessed with timely rains this summer.