I'm no expert on stocking, but I had 6 ghosties in my 4 gal with my betta Goblin. I mean only two are left because be was nomming on them when I went away on the weekends, but they are cute and fun to watch. I would test out a few with your betta though after a water change. He can think they're a delicious snack.Gandalf is in a 2.5 gallon and Sookie is in a 3 gallon. Is that enough room for them and shrimps?