did anyone ever say the water is crap?
You are new, so I will explain something. The 5 gallons are a very small amount of water. It is easier for a tank so small to get messed up with the levels and all. Also sence tha tanks is so small you cant have that many fish in there.
Now a hex is even worse, as there is a small foot print, and the fish dont have much room to move, basically swimming up and down. that means that you can have less fish. There are very few that you can keep in such a small tank.
Now when it comes to the filter, it doesnt make a diffrence of the typoes of fish you can keep or the numbers in such a small tank.
Personally I think that a female betta would be nice in that tank, then maybe two ottos, but that really is about it.