Do I need a filter with live rock?

[goldfish freak]

Ok, I am entertaining a few ideas for a fish only saltwater set up. The tank will be a 4 foot long 120 gallon tank with monos and a puffer. I have read that live rock acts as a filter in saltwater tanks. If this is the case do I need other type of filter, or would the live rock be sufficient? Also will I need a protein skimmer? I am also thinking of adding a serpant starfish or and maybe some shrimps and or crabs to keep the substrate clean. I am not really concerned about the puffer eating the shrimp or crabs since I've had a few ghost shrimp in the tank with him for a while now and he does not bother them. What would be good filtration for this situation, that would not cost me a fortune? Thanks.

 

[FishBait]

Depending on how many fish you're gonna have, and the type of puffer you get, you will need some decent biological filtration to keep ammonia/nitrite in check. Live rock does a very good job at this, and a fine sandbed does an even better one. However, you don't want too much rock so the fish have no room when they get larger, and I don't know if any of them will dig around in your sand alot. I still think a modest amount of live rock, maybe even just a shallow 2" sandbed should perform good biofiltration for you. You can still run an external powerfilter for periodic mechanical filtration if you wish, and it will also serve as added water movement. So at this point it's not necessary, but you could always use one w/out any filter media in it for movement, then just add some pads or carbon for periodic cleanings.

If you aren't already planning, I'd look into a sump as well. Great for increasing water volume of the system, and gives you a place to keep the equipment out of the puffer's "playpen." This is were you can keep the protein skimmer, which I'd recommend you'd get. I myself use the Turbofloter 100, but there are other really good choices for a tank your size as well.