You'll probably have trouble adding fish into the tank with that yellow tang. If it's been there a while, I'm sure it claims the majority of that 90 as his territory. When you decide to add another fish to the tank, either remove the tang for a while, or rearrange the LR. Rearranging the LR will confuse the tang, and he will likely ignore any new addition. As far as fish there are several species of wrasses that would be a good addition. Maybe a sixline, or fairy.