I have been looking into color enhancers for a long time since my Golden Checkerboard was turning orange. What I have discovered unfortunately is there are additives in every commercially prepared food. I even went as far as asking Forrest Teo, Kenny's exporter about his Aqua Bites. There are different kinds of enhancers - you will see things such as "natural marine" meaning shrimp, krill, etc.. asthaxanin is a natural red enhancer as well as spiralina. Other foods may have food coloring or other synthetic colors. I am no expert but I would imagine these are in very tiny quantities like additives in our food. I personally avoid them in my opinion natural is better for us. I know you give your fish an excellent variety of goods so any one food should not give you any trouble. I seem to remember they eat better than you do some nights! This is all IMO though, let's see what the others here have experienced.