Yeah its very fustrating, goldfish are often sold as fish for small unfiltered bowls but in reality they need a strongly filtered tank and the minimum tank size for any coldwater fish is 10gals, for goldys its usually 10gals plus 10-5gals more for every other goldfish you have. If well looked after they can often live to 20-30yrs old.
Basically though when it comes to testing water quality, ammonia and nitrites should be 0(with no exceptions) and nitrates preferably kept under 40(but you should at least have a trace of some)- if ammonia or nitrites exceed 0 you should do a 30% water change with dechlorinator imediatly, nitrates can be lowered by either adding live plants to the tank which absorb nitrates or by doing water changes
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If you need to clean your filter out, never clean it out in tap water as tap water contains chlorine which will kill off the beneficial bacteria that resides in your filter sponge that breaks down ammonia, nitrites and nitrates. You shouldn't need to clean out the filter sponge more than once every 10days- never use nitrates/ammonia/nitrite removal chemicals or ph altering chemicals as these mess up your tank enviroment and cause much stress to the fish.
As far as tanks go though, the only tropical/coldwater fish that can live in an unfiltered tank or a tank under 5gals is a betta, but that is purely because they have been bred in tanks like that for hundreds of years and have grown accustomed to small unfiltered tanks- unfortunatly this is not the same for goldfish.
As for the swimbladder though, just keep your water quality good and cystal clean, feed the goldfish some peas and continue treating the fish with the med and it should recover within a week or so
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Goldfish are quite prone to swimbladder disorders due to their extensive breeding and ability to chow down endless quantitys of food, as long as you don't overfeed the fish and do the above advice all should go fine though, good luck
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