I'm setting up a 29g for a pair of angels that have mated. I'll be using a large sponge filter and no substrate. First, where should I put the filter? I'm leaning towards a rear corner. Should I put it elsewhere? Next, should I run an airstone in addition to the one in the sponge filter? Next, heater. The back wall would be the normal place, but I had a thought of putting it on the floor or the tank. Good, bad, crazy? Any other suggestions?