I used canister filter or sponge filter in my previous tanks and they were both good, but I changed them for a built-in filter in the newest one. I I divided a not too wide parcel with a large sheet of glass parallel with the back wall of the tank (130 l), and then I made smaller parcels with different filter materials too, just as it would be a canister filter. The water comes through a sponge sheet and a small, cheap water pump lifts it into the filter where it runs through the parcels in a zig-zag way and runs back into the newt-keeper section through a piece of plastic mesh at the other end of the aquarium. The living area of the animals became smaller approx 20 percent, but the filter works fine with the large surface for bacteria and it was much cheaper than a real, large canister filter, plus the current is minimal because of the possibly smallest water pump. I change water quite rare, maybe once or twice in a month, but the water parameters are still all right. I built it because I couldn't use living plants nor substrate for a reason, so the simple sponge filter would have been too weak for the job I think.