Depends on the type of filter...do some google searching on aquarium filtration, you'll find more than enough to fill your head in a hurry!
However, some quick points for the beginner:
Mechanical filtration - Goal would be to remove large debris from the tank/water, usually something like a Hang On the Back (HOB) filter.
Biological filtration - Goal here is to promote the nitrification process, turning ammonia (i.e. decomposed fish waste, uneaten food, dead fish/plants) into nitrite, then into nitrate - which becomes plant/algae food. An example might be a wet/dry filter or a sponge filter.
Generally you want a combination of both...because the mechanical filter won't help you with long-term ammonia levels, and you don't generally want to wait for a biological filter to decompose large, visible fish waste. I like to use a combination like wet/dry + can filter...or sponge filter + HOB.
Ultimately the goal is to keep your ammonia and nitrite levels at zero, and your nitrate level at whatever you deem acceptable for the plant life you have in your environment. Note: if you don't have live plants, then by default you'll have algae - that's just Mother Nature's way of handling nitrates.
Again, go poke around google and read to your hearts content. You'll find lots of articles on what's the best combination, how much you should have for what size tank, etc. And of course, ask here for more specific details!
However, some quick points for the beginner:
Mechanical filtration - Goal would be to remove large debris from the tank/water, usually something like a Hang On the Back (HOB) filter.
Biological filtration - Goal here is to promote the nitrification process, turning ammonia (i.e. decomposed fish waste, uneaten food, dead fish/plants) into nitrite, then into nitrate - which becomes plant/algae food. An example might be a wet/dry filter or a sponge filter.
Generally you want a combination of both...because the mechanical filter won't help you with long-term ammonia levels, and you don't generally want to wait for a biological filter to decompose large, visible fish waste. I like to use a combination like wet/dry + can filter...or sponge filter + HOB.
Ultimately the goal is to keep your ammonia and nitrite levels at zero, and your nitrate level at whatever you deem acceptable for the plant life you have in your environment. Note: if you don't have live plants, then by default you'll have algae - that's just Mother Nature's way of handling nitrates.
Again, go poke around google and read to your hearts content. You'll find lots of articles on what's the best combination, how much you should have for what size tank, etc. And of course, ask here for more specific details!
