Posted: Mon Aug 14, 2017 4:19 pm Re: Hello everyone!
What hole in the side are you referring to? But yes, I would use a canister filter for both of their tanks. The hang-on-back filters are okay for extra filtration, but not good enough as a main filtration method with turtles. Also while the tanks are 75 gallons and 20 gallons, the water level is very low. Does the water stink? I can't imagine the hang on back filters are adequately keeping the water parameters at safe levels.
Angus going back into the wild is certainly a risk. A wild vs captive animal are very different in behavior. Plus, as you said, he is family.
Have you considered, as mentioned earlier, getting stock tanks for the two? Stock tanks tend to be wider than aquariums, so they provide even more swimming room.
One last thing, is the lighting you are supplying UVB lighting?