Yes, most filter media used in canisters will start biological filtration within 2 wks of use which in turn means you'll be manufacturing nitrates. I have a 404 too and right now I'm basically going to try it out as a carbon filter for when I want to use carbon; otherwise I'll use it empty to power my UV. Additionally, any media you put in a canister will, within 2 weeks, become a biological filter, including carbon, nitrate sponge, filter pads, floss, etc., which you want to avoid.
I'd suggest that, if you haven't unpacted it yet, you return it. You can use a smaller canister to do carbon filtration and, even with that, you will want to either change out the carbon every 2 wks, or remove the carbon altogether until you need it. Now, I know people put LS and LR in the canister, but I don't see how LR will live very well in a dark canister, and the grains of LS are so miniscule that I'd think you run into a problem clogging up the motor in the canister. Better to put what little LS and LR you can put into a canister, directly into your tank or sump [if you have one]. Canisters, I believe, are virtually obsolete for the marine hobby, except, as I said, you can run carbon thru them.
[ May 11, 2001: Message edited by: Beth ]
