Most people complain about tangs getting paler, not yellower! Tangs need a lot more than flakes and frozens...in fact, I won't really recommend flakes as a stable for tangs. These are vegetarian fish, and need greens, greens, greens. SeaWeed Select is a good choice here. Frozen food, IMO, is mostly moisture [read the lable] and flakes, though the lable reads more nutritional value, they tend to pollute the tank if anything gets left uneaten.
Tangs are also grazing fish, which means they pretty much want to be eating their greens all day. A seaweed clip with Seaweed Selects would be a good idea.
Usually yellow tangs are kinda brownish [spotted] first thing in the morning. Is this what you mean, or is he just a richer yellow? If he is just a deeper yellow, I say you must be doing something right! If behavior and eating is normal, then stop worrying and enjoy this fish---yellows are beautiful creatures.
If the color is actually abnormal, consider any immeidate changes you have made to the aquarium. Add lighting lately? Change your MH bulbs? More lighting and a resent bulb change of MH's can cause some shock.
[ May 17, 2001: Message edited by: Beth ]