Supplemental food needs to be given as you would any animal. Each time we feed, we give the cat food first then as the fish are slowing their feeding cycle- we add the duckweed, carrot stem etc. that gives them the opportunity to feed choice on the roughage. We feed our systems 3 times a day average. Cat food seems to have a higher content of fat compared to some feeds. One drawback we have seen has been depending on this fat content, you may get an oil film on the top of the water. This film has not affected our systems at all. However, I would be open to finding a source for a vegetarian based food that is not GMO. What we are using is generally minimal ingredient or sometimes non-grain based cat food (dick vanpatton, taste of the wild, etc)
Our fish love certain types of leaves- carrot tops are a special treat- tie up so they don’t get stuck in the filters/pipes. We have tried SFL, but as a large portion of the diet in whole form it did not work. We even tried making a feed and baking it, but boy was that a horrible smell. The boss won’t let me try her Excaliber dehydrator to make fish food for fear that it will be ruined, but I probably have 5 lbs of frozen sfl that I would love to try and incorporate into some sort of meal.
Davidscldfl has had great growth with his fish using the Purina- I just can’t get past the GMO soy, wheat and corn which I refuse to eat- so I will not feed it to the fish. Jackalope sells the Aquafarms feed on the DIY site which seems to be better than Purina or anything else for that matter, and I have contacted him about his feed, but though they try to use non-gmo sources the soy- a main ingredient- is still gmo because he has a problem sourcing non-gmo. I have contacted several vendors about food sources, but have not been happy with the response, so thus far I settle for the cat food since I feel safe with it. If I could find someone with a peletizer- we would be best friends!! LoL. In any case, I have eaten tilapia all my life and I don’t mind it- though I do notice variances in the flavors, my wife doesn’t really care for it unless it comes out of our system- the taste is pure, clean and sweet, and the texture is flaky- superb. She swears everything else tastes muddy.
This winter we have catfish- a first for us. We will see if the feed changes the flavor of a usually dull, musty flavored fish. There are multiple studies which touch on this subject, with a basis for the taste related to bacteria (http://www.uaex.edu/aquaculture2/FSA/FSA9051.htm) or algae blooms in aquaculture.