hmmm it is possible to cure it, but not in all cases. bit of a bugger is swimbladder cos by the time you see any serious symptoms of it it's very often too late. You do need to look at why they've got it though
sometimes they will be born with a deficiency and then can have problems but still lead a relativley full life, one of my dad's fish (can't remember if it's a koi, goldie or shubunkin... anyway) has always had it, swims like a bit of a spaz but as long as you make sure he has enough food he's fine, good few years old now and still doing alright, maybe won't make it to 40+ like some goldies but he's not doing badly.
other times i've had a perfectly happy healthy fish suddenly develop it, start swimming funny one day and the next they're dead, nowt you can do.
dunno about the pea diet, never heard of that before. there are meds on the market that say they cure it, i've never had sucess with them but it seems others have so maybe it's worth a shot.
I'd post in the emergencies section if I was you, there will be people there who know more about diseases and meds than i do.
good luck