you could through in a snowflake eel, maybe 7 small damsels, a lawnmower blenny and maybe a pygmy angelfish with that size tank. For filtration you would need to up you bio filtration. If i were you i would just about 60 lbs of live rock. you can get away without having a wet/dry. you would also need a med size protien skimmer. Don't get a puffer because they emit a toxin that would overload your protien skimmer. Salt mix, hydro meter, test kit and your good. To start, completly strip down and clean everything, and new substrate and water, then all the live rock. The rock has to cure so keep 12 hours of light then add 2 damsels about two weeks later. Add the rest of the damsel then the eel. And read about it because even with fish only with live rock tanks you just cant switch it on a dime.... Good luck!