I have 2 penn plax cascade 700 canisters each on a 38-40 gallon tank. Media used bottom to top: Course sponge, filter floss, biomax, filter floss (if it fits) The other day I did filter cleanings on both, and am wondering if what I found was normal or if I have something wrong. It's been about 1-2 months (terrible memory) since they were cleaned last, for 1 this was the first cleaning since set up. The sponge doesn't seem dirty, the biomax looks fine, but the filter floss is almost black. In my established tank I replaced 1 pad, then laid the old ones at the bottom of the canister, under the bottom basket, to make sure I kept plenty of bacteria. The other one I replaced two filter floss pads. I dosed ammonia (I can't even remember how much) and had a massive ammonia/nitrite spike. I have removed all stock from that tank, so I'm not worried about the spikes. They are already starting to go away. But is this normal for the filter floss to get this dirty? All information I find on these filters is that they filter from bottom up, but the original instructions had floss, carbon, then sponge. I'm assuming they meant for the sponge to be biomedia? Or should I switch everything around?