I have a 4 inch gold gourami and a 3 inch angelfish in a 30 gallon tank (I'll get a bigger tank when they grow larger). My question is how to get their color's to be more vibrant. At the moment, the gold gourami is a pale white-ish yellow color and the angelfish is plain white with some small black stripes. How do you get them to be more vibrant (especially for the gold gourami)?