subliminalanarchy said:A skimmer is highly recommended for any tank over 30g's. And you should still be able to use your filter as long as you're cleaning it out every week or so. If you're going to get a sump you could put live rock in there for extra biofiltration or you could get a fuge going.
David S said:You don't need a cannister filter but it's worth using with filter floss as a vacuum cleaner on your tank without removing any water,also a good way to utilise any chemical filter media when needed.
What size sump and whats going in it?
cmor1701d said:SW or FW?
What's in the tank?
What do you want the tank to end up looking like?
What is your old filter?
You do not NEED a skimmer, but if you are planning a reef tank it's a good investment. It's not needed day 1, but you should leave enough room to add it later.
subliminalanarchy said:As long as you have enough live rock you should be fine without the filter. You shouldn't be relying on it anyway, it should only be used as an extra precaution.