The only tang you really going to be able to do in that tank is a royal blue. Adding a yellow may be okay but i know its a war waiting to happen. Radiant wrasses, sixline wrasses, fairytale and/or lyretail wrasses are my favorites. Butterfly fish are cool too, and look awsome in a properly stocked tank. triggers would be fine, and you would need to get some larger wrasses to cope with the trigger. I have known some triggers to get fusy about tank mates and needless to say, they are no longer in that tank lol.