I have 1 ADF in my 10gallon with 3 platies and a guppy. Other peaceful community fish would be a good match, what size tank are you looking to get? Be sure to avoid a tank that is too tall as they have to swim to the surface for air. I use gravel in my tank with no issues, I’ve heard to avoid anything small so they accidentally eat a piece of substrate and choke, I’ve never had experience with sand though. If you decide to include them in a community tank, I’d recommend feeding them their food (I use frozen bloodworms or brine shrimp) with a turkey baster because they are slow eaters and the other fish will eat all of it first and he could starve. Also, be sure you have a secure lid with no open areas, they can escape! I used to have 2... one was found on the floor all dried up after I noticed him missing for a while
Good luck, I love the little guys, they are cute and fun to watch.