Another thing to keep in mind is that if you have any type of closed loop, you'll be adding nutrients by default. For example, if you have the food waste -> BSFL -> fish -> plants -> harvest loop, you'll be adding food waste from outside the loop, which will have the nutrients you need. If you continue consuming bananas, banana peels will be an excellent source of magnesium and potassium that will make its way into the plants through the loop mentioned above.