i have a medium sized bimac mantle is probably about 3 inches long 2 inches wide usually, not sure about tentacle span. but i have him in a 45 i no its a little small but i could not fit n e bigger. running on it i have an eheim 2229 wetdry canister and an eheim 2215. in the 2215 im only using pads for mechanical since i have the wetdry for biological. im thinking of either taking the 2215 off since its holding soo much nitrates or possibly filling it with chemipure and maybe some other type of absorbant filter. do any of you have any suggestions on how to keep the nitrates down or have a problem with nitrates as well.