Your jardini would be much better off in a tank with at least 30" in width. IMO a 30" jardini would not be very happy in a 24" wide tank. As for the P-bass I think most could outgrow either tank(may want to post in p-bass forum for comfirmation). If your do attempt the combination btter make sure you have a tank divider handy once the jar gets to be about 10-12".