04-10-2010, 11:45 AM
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The choice of filter for an aquarium should be based on the fish that will be in the aquarium. Not all filters suit all fish, due to their effect on the bio load, stocking numbers, requirements respecting currents, etc.
A 150g tank of small forest fish (tetras and other characins, rasbora, angels, discus, gourami, most catfish) needs minimal water movement; some specific fish within this group require slightly more current, and it is usually easy to accommodate them within a large tank. And such fish usually require planted tanks, and excessive water movement is detrimental to plants as well as these fish.
On the other hand, a 150g tank of larger fish like Central American cichlids would want more filtration to handle the biological side of things.
All of my aquaria are planted and contain forest fish so a canister rated for the aquarium size is sufficient. In my 115g for instance, I have a Rena XP3 and the filter return is at one end of the tank and I left off the spray bar so a bit of a current is established at that end (it dissipates quickly in a 5-foot tank) which suits the woodcats in the wood under the spigot as they like a current, but the cardinals that do not are happy in the rest of the tank where there is very little movement.
Once you have an idea of what fish will be in your tank, it will be easy to decide on an appropriate filter.