Welcome to AA! I like Oki for a fish name.
Is the turtle in the same tank as the betta? I hope it's okay if I offer some advice on your brother's tank--goldfish need a bare minimum of 30 gallons of water per fish as juveniles, depending on the species. Kept in too small a tank, goldies become stunted, meaning that their outsides stop growing but their insides don't and they suffer terribly.
Anyway. You didn't ask for advice on goldfish, sorry. Just wanted to suggest a possible tank upgrade for the fish's sake and for yours, so you don't ever have to see them get sick, which is so difficult. Again, welcome to AA. People here are really friendly.
Can't wait to see pictures of Oki or Puddle!