OK, at the risk of losing any respect I might have earned in the past, I am going to be totally honest and, no pun intended, "come clean" on this one.
I go months and months without cracking my canister filters. My tank is overfiltered, having two fluval 404's on a 55, and I water change a lot, say 40% once or twice a week. Y'all have seen my water change system, so you can understand why big frequent water changes are no big deal for me, but why gravel vacs and filter maintenance are more work. So, just a few weeks ago I realized that I had one fluval that had not been opened for 5 months, and one that had not been open for 4 months. Flow from these filters was still robust. I opened and cleaned Both of them. What I found was that the fluval pre-filter sponge was just a bit browner near the top edge that the water passes through first, and that the browness had traveled a few inches further from the top than when I had done this maintenance every other month. Other than that, mechanical filter ceramic rings (2nd layer of mechanical), my filter floss (3rd layer of mechanical) were still rather clean. The mechanical filtration rings were rinsed in tap water anyway, and the floss was replaced anyway. Yes, the mechanical filter rings were rinsed in tap water because they are for mechanical filtration, the biomedia above it will be left alone. Above those two baskets, I have two baskets of porous bio-media, which were really clean. These were taken out and inspected, but then put back in with no rinsing. The pre-filter sponge was rinsed and cleaned in tap water, then put back in. The fluval lower canister was left with most of the tank water in it, so that I could reinsert the sponges and baskets back into the tank water left in the canister. The impeller was removed and cleaned, but there wasn't much of anything in the impeller chamber.
Wait! above I stated that I would be honest, so I have to admit that it had actually been 6 and 7 months since I had last cleaned the fluvals. Now, I am rather embarrassed that I had gone over half a year since maintaining my filter, and I have made a vow never to let so much time elapse again. Of course, when I first set up the tank I did do it monthy or close to it, but, well, you know, sometimes things can get away from you. But having done this, I was amazed at how un-dirty the filters seemed to me. I am not particularly overstocked, I don't over feed (not much, anyway), and I do a lot of water changes. Perhaps these good qualities have enabled me to neglect my filters. I am not recomending that you go 6 months yourself, but I would not feel guilty if you haven't done it monthly, providing that when you do open it up, things aren't really bad.
