Hiya Wiseman4400, as you might of noticed this is not a chatroom forum , It takes a while before you get a response but if you check back everyonce in awhile we do answer. Welcome to MFK by the way.
Your red belly is probably a nattereri and can get to 14" long but usually don't get bigger than around 9-10". A standard 29g is 30" long, 12" wide and 18" tall. Even keeping just the one you should get a wider tank, Glasscages makes a tank that is 36"x 18"x 13"tall (40g) for $60 that would work great for you. Hope that helps.