Our fish in the hobby are either grazers or gorgers. With most being grazers. Grazers have small stomachs and spend much of their day foraging for food, eating small bits here and there. Gorgers (typically much larger fish) will eat a large amount of food, then not eat again for quite some time. Since most of my fish are grazers, with many fry and young fish growing out, I feed several times a day IN SMALL AMOUNTS. I see no advantage in fasting fish one or more days a week, Although I have withheld food for 2-3 days prior to bagging for auctions with no apparent ill effects.
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I wrote an article, published in our clubs publication, regarding commercial fish foods. In the old days, many foods were made with low quality fish meal (e.g. cannery waste- head, bone, scales) with a LOT of grain/grain starch as binder/filler. These days, many high quality foods are made from WHOLE fish meals and these can be just as good as foods made from fresh fish (which may or may not be WHOLE fresh fish!). So there are many high quality commercial foods available. BUT you must examine the ingredient list.
There are many good foods: Omega One, New Life Spectrum, Cobalt, Ocean Nutrition, Tetramin, Northfin, to name a few.
I blend 3 high quality foods and augment with cultured live foods and on rare occasion, frozen food like brine shrimp.
I think a good stable diet of nutritious food negates any need for special food for color. Color is often a function of genetics as much or more than diet.
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