Canister filter question

[Turin Turambar]

It's a question about cleaning.

I read on many sites (also Eheim official) that canister filters need to be cleaned in 2 months - minimum!

That's quite lot of time for me. Currently, I have an external hang-on power filter for 40-100L tanks and I clean it every 7 days (I have a 60 litre tank)! Every 7 days and it is full of dirt. Not that it is cloged, it's not, but I cannot imagine leaving the stuff there for 2 months minimum! I mean, great - especially when I'm on holidays and similar, but the canister model I was looking for was only 1.5 times bigger than mine!
So how come that canister filters need such infrequent cleaning times? What about dirt and small plant particles left there for a few months?
Thanks.

[Matt W]

I find that I clean my canisters ever month or so, sometimes a little sooner. I don't think there is any harm in cleaning it more often than needed. Really, you just need to determine how dirty yours gets based on the fish load and whatnot you have. I would install the new canister, let it run a couple weeks and check it. If you deem it needs cleaning, go for it. If not, close it back up and check again in a week. Repeat until you determine how long you think it should go.

One reason I think that canisters will go longer is that there is more filter media in there. I know in my Fluval 304, first you have that huge sponge, then I run two baskets with filter floss, then my biological material. With that much filter media in there, it is bound to go longer...

[NickH]

Canisters can go much longer than HOB filters between cleanings. The increased media capacity and the no-bypass nature of the filter make for more contact time between the water and the nitrifying bacteria. Flow rates are much less important for canisters than HOB's. As long as water flow isn't severly impeded, it's good to go. Actually, the "dirtier" it gets, the better a biological filter it becomes. You don't want to tear the filter down in short intervals, because it will ruin your nitrogen cycle. Given the right conditions, canisters can often go 3 - 6 months between cleanings. This is for an appropriate size canister for the tank, moderate stocking level, normal feeding and regular water changes.