I think two filters would be to much and a waste. My buddy had a ac50 on his 55 gallon and it was crystal clear. Im putting a powerhead for circulation to
run the ac110 or ac500 wichever ya wana call it run dubble sponges in it . means u have to buy a extra one. and run a powerhead in the tank. and buy another ac110 spong stab it on the long end with a knife and slide over the input of the powerhead. u be fine
I run 2 AC 110's on my truvu 75 long along with two powerheads with sponge filters on either end of the tank mounted for maximum surface aggitation. My tank is stocked pretty well. Running two gives you some choices on media such as filter floss. I have been running this same set up for more than 20yrs, never a problem, always a crystal clear tank and happy fish!