Is there anything else i can do to save my black moor fish?

for the past month my black moor fish has been floating and swimming on his back, think it is swim bladder as no other signs. i have always fed my fish a varied diet of flakes, frozen blood worm and peas, they also have live plants in their tank. i have also used swim bladder treatment but with no effect, and have brought a much larger tank for the 4 fish. my last bubble eyed fish died of this and i do not want this one to die to... i love my fish. what else can i try?!?!