The only filtration needed as the others have said is live rock and a good protein skimmer. The skimmer should be oversized if keeping a high bio load (lots of fish). Filters commonly used in freshwater tanks such as HOB and canister filters can become nitrate traps if not cleaned very often; this frequent cleaning can also kill the good bacteria the filter provides if not careful, making the filter useless. A sump filtration system would be good as well simply because it will increase the water capacity of the system thereby helping the prevent nitrogen(ammonia, nitrite, nitrate) spikes.