Bettas and Goldfish
Oh, one last thing, I hope its a large tank cause these are all pretty dirty fish. If its not a large tank I suggest replacing your water about weakly to ensure that your Bettas colors stay bright and that all the fish live long healthy lives.
Good luck!
Betta fish usually like to be in small bowl by themselves. You can combine them if no problem occurs. If Chelsea starts attacking the other fish, then I would put him back to his separate place.
I really don't recommend it.
While Chelsea may *seem* fine in the goldfish's water temperature, you can't really change an animal's natural needs, and he would still much prefer tropical temperatures in the high 70s. (You will need a heater for this.) He's probably just putting up with it, but if you put him in warmer waters you will most likely find that he becomes much more active and healthy.
The situation might appear alright to you, at least in the short run, but at the end of the day, goldfish are still coldwater fish and bettas are still tropical fish, and you can't change that.
Betta+Goldfish=Big problems!! First of all, goldfish are coldwater fish and bettas are tropical fish. Goldfish can't handle the high temps that bettas need to live in. Second, Bettas don't like any kind of brightly colored fish in their territory. Mr. Goldy will surely be picked on and beaten to death. Second, Goldfish have a tasty slime coating that makes them even more likely to be picked on because the betta will want to try and taste him!! It's just not a good idea at all.