Soft shell turtle habitat

I keep one that a neighbor raised from very young. Have him in an aquarium with turtle sand. Previously he was in gravel too heavy to bury himself in.

Was going to release him into the wild but afraid he won’t survive.

He is thriving and growing, but maintaining the filter is tough.

I’m getting a larger 30gal tank and wondered if there is a filter setup that works better in a fine sand environment? Any ideas?