Do you?
Let me pose a scenario to you: you have an 80 gallon tank with a couple of angelfish and nothing else. What is the bioload like? Now take the same tank, and put in large silver dollars, large cichlids, and large plecos. What is the bioload like then? I would recommend that you never ever ever listen to the "gallon" rating of a filter. Any appropriately sized, and biologically mature filter should be able to handle the occasional over feeding. It doesn't sound like you over fed at all really. This leads me to believe that you are probably near the limit of the capability of your current filtration.It's not the penguin, it's two emperor 400s with the biowheels, both certified for up to 80 gallon tanks. Filtration is definitely not the problem, I know that for sure.
Anecdotal evidence never amounts to much.Yes...I've seen more cichlids in a 75 with less filtration..completely fine. It all depends on feeding and water changes. I feed super lightly, I always want my fish hungry so they never expect food. In nature fish look for food, always. So by feeding lightly I keep them active, and there is never left over food in my tank.
Anecdotal evidence never amounts to much.
What stock have you got in the tank?
This isn't exactly correct. There are too many variables that affect how well a filter actually works. No reviewer is going to be able to exactly replicate your setup, stock, feeding and maintenance schedules, and water conditions. All of these things can dramatically affect what a filter does for you. Anyways, that's my 2 cents. Pic for happies.anybody with google can figure out the capabilities and limits of filters for their tanks.