Hagen AquaClear 20 Aquarium Power Filter?

[TJT]

You need a sponge and a bag of activated carbon. You can also add a bag of beads that removes ammonia (optional). The sponge you can clean it every 2 weeks an replace it every 2 or 3 months and the activated carbon clean it every 2 weeks and replace it every month or month and a half.

Not at all true. The aq filters come with a 3 stage basket. The 3 stages included are 1 sponge, 1 carbon pack, and 1 bio pack. I always buy an extra sponge pack (3 included for a couple bucks) and run 2 sponges, and the bio-pack. Ive had my aquaclear 20 for a few years and still run the original sponges. I liked it so much that I bought a aq 50 when I was given a 29 gallon with a whisper filter for replacement.

 

[Wateveryousay]

So having all three stages prevents algae from growing?

 

[TJT]

the stages have nothing to do with algae. sponges are mechanical filtration, carbon is chemical filtration (generally considered unnecessary, useful for use after medicating a tank though), and stage 3 is biological, for the nitrate cycling bacteria.