Some products are snake oil like aquavitro fuel. I saw no significant difference when using fuel. However I saw an improvment in coloration when I started dosing amino acids but I do have a unls tank. I have tried a several brands and there are only two I have any faith in. IKE is right that amino acids can be produced by the coral, but amino acids also exist in the water column in and around reef structures in the ocean. IKE is right no one has been able to prove beyond a doubt that corals have the ability to incorporate these into their structures from the water column only that they exist in the water column. I see a difference in a low nutrient system and find it less risky than feeding a bunch of food. just my .02