I believe my fish have some sort of swim bladder disease. They were swimming all weird and floating straight to the top whenever they weren't struggling to stay down... then when I fast them if goes away. BUT as soon as I feed them, even once and even a tiny bit, it comes back right away. They are 7 year old goldfish... 2 of them in a 20 gallon tank. We had one pass away recently (6 months ago) as well, unfortunately. Anyway I can't keep fasting them and not feeding them. I've tried 3 different kinds of food, and also peas too. Anytime they eat ANYTHING they float up to the top and swim sideways. Should I try treating them with an antibiotic? Could this be some sort of infection that I should treat. I feel bad starving them so much, and I feel bad feeding them cause they can't get their swimming right. Can someone please help?