I started off my aquaponics with Seasol fertilizer. I currently don’t have any fish in the system, as I have not been able to source any (the hatcheries are all sold out). I’ve been running on a pure source of ammonia, checking levels daily.
Some of the newly emerging leaves have yellow edges. Normally the waste from the fish provides the ammonia and other nutrients required. Sometimes potassium and iron can be lacking, which can result in leaf yellowing.
Some web sites suggest adding a few rusty nails along with seaweed extract. I have added the seaweed extract, as well as some iron chelate mixture. This has solved the problem.