water changes

[madison133]

hi
my son and I started our 50 g reef tank in Jan. We have 85 lbs live rock. Some mushrooms, polyps, a toadstool, one flame angel and a parasite eating fish, two hermits and a starfish. Plus I hate to admit but we still have one blue damsel that we couldn't catch. He gets along with the angel.Everything is doing well so far. We have been changing 10 gal of water weekly is this too often? Also, we usually have the water ready days before, but should I worry about the temperature of the new water? Plus, any suggestions on our next fish. Thanks for your help.
Linda