Originally Posted by ILLBETHEJUDGE
That is the purpose of the filter having an intake. That is what the filter cartridge is there for, to trap all the dirt, but please correct me if an wrong.
I was thinking about using 4 aquatech 5-15 but I don't know if that would keep my tank clean.
I understand what your saying now but I wouldn't exactly use the term dirt. There shouldn't be any dirt floating randomly throughout your tank, that would clog up the filter in no time (not too mention stress out the fish and potentially harm their gills). I think a different way of putting it would be that the filter sucks up small particles and traps them whether they be plant matter, fish waste, uneaten food, or particles of dust. The charcoal (if used) absorbs chemical impurities.
Pre-filters are great. They trap particles and waste while also housing beneficial bacteria. The fact that they trap stuff before it goes into the filter cartridge is actually a good thing because it extends the life of your filter cartridge and filter media by reducing the time in which it takes to clog. Which leaves the charcoal and beneficial bacteria in the cartridge to do their job better and longer.
Just clean your pre-filter every so often by using a cup or a net to trap the particles stuck to it and gently sliding it off of the intake tube. Then just set it in a tub or bucket of water from the tank (to retain the beneficial bacteria) and give it a few squeezes and rub larger particles off of it. Then slide it back on and your done.
Personally I am partial to sponge filters. Look into this if you want, they have sizes to 55 gallons and larger while being safe for the delicate fins of a betta. They creat little to no current at all and the bubble can be entertaining to both you and your fish. http://www.atisponge.com/hydro-sponge/