Once I tried the Penguin filters, I stayed with them as long as I had my 30 gallon tank (about three years). The filters are relatively easy to use, although installation can be delayed a little when the outer edges don't properly align for placement. Excess food and fish waste accumulate on the filter and can be rinsed off occasionally to extend the filter's life. The filters are on the expensive side, but they do a good job and the added expense is a good investment.

Pros: Holds the "gunk" and lasts fairly long

Cons: Can be a little difficult to align/edges get caught

These things last forever! It say to change it every week or two but I do it about twice a year :-) They are pretty cheap, too. They are about $4 at PetCo, so I am sure they are cheaper elsewhere!

Pros: last long cheap

Cons: none

easy to use and makes the water really clear and clean. it's the only brand i used on my fish tank because i've always heard it was the "best".

Pros: lasts a while

Cons: kinda expensive

Just take your old filter cartridge out and put the new one in. It cleans your water fast and makes it look crystal clear!

Pros: Cleans water fast!

Cons: Can clog quickly depending how dirty tank is.

This product does a great job of keeping my two aquariums clean, I use them with my 55 gallon and with my 150 gallon

Pros: convienient

Cons: needs to be replaced every couple of weeks