So I am planning on upgrading my girl Shimmer from a 1 gallon to a planted 3 gallon critter keeper with a heater. I also want to get a halfmoon or PK from PetCo. What would be a good heater for a 3 gallon critter keeper? Also often PetCo's bettas are sick, so should I plant the PetCo betta's 3 gallon critter keeper? Or leave it blank as a hospital tank so I don't have to throw out plants? Thanks for the help guys! I plan to go get the new betta this week and put it temporarily in one of my old 1.5 gallons.