What happened with the dats? Don't worry about its feeding habits yet. Some go on 'hunger strikes' for a while after being added or when stressed. Welcome to the best sub forum on mfk, by the way
Once your other two are comfortable they might start swimming around. After settling, activity levels, in my experience, have a great deal to do with the aquascape, number of tankmates, and amount of food they are consuming.
Good luck!
Lol have you even pellet trained dats that was a pain in the rear 4 months to get all 5 on pellets. The smaller poly started eating the moment they went in the tank the 8 inch del has yet to eat only been 2 weeks. My wife deals with all the tanks doing the week since I'm work nights plus 5 12 hour shifts a week. She likes the poly but the no eating is bugging her big time she got so mad with the days hiding she sold 4 of them for only 200 ranging from 6 to 9 1\2 inches.
Sent from my SM-G900V using MonsterAquariaNetwork App