Depends on what type they are. Carnivorous (examples – trout, perch, and bass) require a feed that has high levels of protein (45 – 50%). Omnivorous fish (examples – tilapia, bluegill, koi, and catfish) require a lower protein feed (typically 32% protein). Younger fish require more protein than mature fish.
While we applaud the efforts of those who try to further “close the loop” by producing their own feed (such as cultivating their own Black Soldier Fly larvae, red worms, and duckweed) we still strongly recommend that you feed your fish a professionally formulated feed. This will ensure that not only do these fish that are in your care receive an optimal diet for their health but that your plants also get a balanced diet through their waste. Please read our post titled “Aquaponic Fish are Not Garbage Disposals!” to learn more.