Do you need live rock ??

Title explains it all could you do a saltwater tank but just use a filter instead of live rock?

 

No, I don't think so.... I think they call them FO tank.

 

IMO live rock is the most important filter in a Saltwater tank

 

Yes, you can if you really want to. Is cost an issue for you?

 

Not so much cost as is taking the time to cure it. If I did make a saltwater tank I would probally give $1000 for a 40 gallon. Not including fish

 

What type filtration are you planning? What type of fish are you wanting?

 

My thinking was a canister filter with some clown fish and something else small. It would be for a 30 gallon setup

 

You can do that although not a good choice to sustain the live stock. Your best bet would be to have about 15 pounds of live rock in the tank with some circulation of power heads, back in the 80's I used a wet and dry fitration with bio balls and sand in the tank but doing it that way takes even longer than it would cycling the rock. The rock will support more so than without having any. In my eyes you may spend the money on the rock but you don't need premium rock you can use rubble in the canister with out anything else in it and add a few pieces in the tank for decoration and will serve as the biological balance of the tank. What you are wanting to do is just like the freshwater applications which use the gravel as the biological side it really doesn't do as well for saltwater but I also am not saying that it can't be done its just not a well balanced tank that way. And is not as strong as if you would use rock.