I am getting a new Betta this weekend to live in a ten gallon with a divder (so really about four gallons), and was wondering any last minute ideas? ( won't have any issues with the filter) The fish will be probably Ct or Hm.
Oh It's been running for 6+ months and is getting ready for another cleaning, i currently have 4 goldfish and I am selling 3 of the 4, and i have researched and looked around for a while, so i am planning to keep just the one fantail in on side (i know most people say thats not a good idea) and the Betta in the other, but we are getting a 5 gallon heater for the Betta side so it only heats his part of the water, and I have had the goldfish for 4 months and can say that he is healthy and non aggressive to other fish.
Your fantail will get to big for that small of a space. What will happen is his body will stop growing but his organs will keep growing causeing him to have a slow painful death. So please rethink this idea. Also if I am not mistaken goldfish produce alot of ammonia which will be bad for the beta. As far as heating only oneside of the tank if you have a normal divider with holes in it the water will circulate through both sides of the tank. Sorry to be the bearer of bad news but I just don't want either if the fish to suffer. I can tell you really care about your fish because you are trying to learn so I am not in any way trying to bash you I hope you do not take it that way. Good luck with what ever you decide to do.
Oh, and I have had 2 bettas before, (3 if you count the class pet i took care of for a year) And I just haven't really got into them this much. the last one I had, Wilson - From castaway, Lived about a year because I wasn't allowed to have a big tank and had him in a flower vase.