Just get a good filter, possibly a canister filter cause turtle loves getting dirty, i myself own a alligator snapping turtle and he is very healthy. But basically just get a good filter, make sure you get something he can rest on completely dry along with a uv
light so that he can warm himself up *crucial*. Other than that with a 75 gallon you won't be cleaning as often compared to the 10 gallon. And welcome to the site i'm pretty new too.