I didn't see the rest of the livestock, i just assumed it was those two fish in a 20gallon. yeah with that stock you need to do a lot of water changes. I understand why you have those fish though they are all really sweet. do you have any coral in the tank? I think that would be a better option if you can't resist adding stuff to the tank. be careful though it is real easy to get hooked on corals, like all of us