To heat or not to heat?
So my friend recently got a 5.5 gallon tank. I helped her get it set up with 2 plants, anubias nana and java fern. Theres also a plastic coral thing and petco sea blue gravel. We got a glo light and an in tank filter, for 3 gallon tanks, because she's getting a betta. We're going to pick up the fish tomorrow and I have a few questions.
First, do we need a heater? We want to get a betta, a few ghost shrimp and a cory or something. We'll also try to get a few more plants, but we're not sure which type yet. Second, what fish would work as tankmates? And third, we got a bottle of betta water dechlorinator, but we still need another bottle. Is it okay to get another bottle with the fish, add it, and while they're acclimating to the temperature, let it settle?