Cataracts on Goldfish?

Question
Hi I have a 30gal, established, unheated, freshwater tank with 2 fancy goldfish, 1 pleco and a feeder goldfish. I also have a broad leaf plant and a whisper filtration system. I've have this combo for the past 2 yrs but the fish in question is the feeder who's 6yrs old! My feeder (Gillagen# has always had a scowling 'I'm better than u' disposition and was the only 1 of 12 feeders to survive. #I wasn't feeding them to anything, I just prefer goldfish# After a few years of different combos he was always the only one to survive. He's still a beefy 5 inch monster but he's slowed down now of days since he's gone blind. At first I noticed a little eye bulging and put him separate and medicated with melafix according to the directions... but for the 5 or 7 days #i forgot now# the bulging only got bigger and Gillagen got more angry. Since the medication had no effect and he wasn't 'sick' per say I figured if this was going to kill him at least let him be in his home. But that was a year ago and he hasn't shown a difference other than the bulge has clouded over. He has two white eyes and swims into things regularly but despite this he doesn't have anything but thick golden scales- hes just swimming alittle slower now. I removed the floor ordimates I had to reduce any damage to him. I always look for anything different with him but hes still him- he used to swim fast across the tank, but now he swims this rollarcoaster ^ kind of way. He even will bob with him mouth open when the latch opens for food. He eats well, I feed lightly morning and night, turn the light on when I leave for work and turn it off an hour after they're night meal. To the point now; should I be more concerned than I am about medicating his eyes? Are the other fish in danger? Is there something I'm doing that caused it? Thank's for your advise in advance... I'm excited to hear your thoughts!

Answer
Angela,    This happens quite often, Storexs sell a bunch of feeders to cycle your tank out and one or two lives and your stuck with a carp that is going to get very big and fowl the water very quickly. Melafix was ok , but this is a mild broad spectrum antibiotic and really needed marycin 2. The damage is done thank osh he has you and you love him. You are not going to like what I have to say next. Your tank is to small. The idea of a goldfish bowl is such a miscoption honey. Goldfish need big water. In fact if you had a pond I would reccomend Gillagen be put in there and he will be fine. He can get huge. The thing is your fancies are they aorands or black mor's if they are going to also get big and in the right water quality you can keep them for twenty years or more. If you want to try medicating him in case he just has cloudy eyes try the maracyn 2, take out the carbon from your filter and after do a 40% water change. This would be in a week. Add a new filter cartridge as to not return the infection back to the tank. I would go up to a 55 gallon tank if you want to keep everyone healthy. Your pleco are notorious;y meesy poopers. So as he outgrows your tank replace him with a new smaller guy. I have had my Black Mor Molly for about 9 yrs now. She lives in a 45 with a pleco I have replaced at least 3 times over the years. She is huge and happy. The medication will not hurt the other fish but, if you have a hospital tank he will absorb more medication and you won't be reaking down your ecosystem. The medication will break doown your bacteria layer but, not much. I personally would medicate everyone. You also can supplement their diet by thawing a frozen pea and cracking it and throwing one in for everyone once or twice a week, that is one a piece. Also you will notice their food is fortified with vitamin C. This is because they suffer from vitamin C defficiency in captivity. You can either get a veggie clip from the pet shop or float them. It is a clip with a suction cup. You can slice thin slices of orange and put it in once a week. They will love you for it!!!!!I would use Marycin 2 , so if you decide to see if this is reversable which it may be let me know how you did. Definately upgrade your tank when you can. Good Luck, Tina