answer:Algae eaters are the easiest way to handle that issue (specifically they’re called plecostomus’). They’re usually dirt cheap for the basic south american common breed. Keep in mind though, they will not stop growing when they’ve reached a max size for their tank. It may take a few years, but I’ve had them reach over a foot long. The bigger issue is that adding another fish will only make the oxygen shortage worse in the tank. How big are the gold fish? The rule of thumb with all freshwater fish is that you want one gallon per every inch of fish. I know goldfish can tend to get quite large, it may simply be your tank isn’t big enough to accommodate them. The quickest fix to this problem (or the only “patchwork” fix) is the air pump like you’ve done. How do you have it set up? Is it hooked to an air stone? How big is the air stone? I would suggest getting one of the long flat ones (10+ inches long and flat, such as this link or this link . The more surface area the stone has, the more it will spread its additional oxygen around. I also would recommend getting a larger air pump than may be originally recommended for your tank, though at 10 gallons I think just about any pump will be built for a larger tank. As far as the infection with the swim bladder. There are various medications you can get at pet stores, especially fish only pet stores. If you have something akin to aquarium adventure (aquariumadventure.com) I would go there. Their staff are usually very knowledgeable on fish diseases and what medication is most likely to help you. Be wary though, I am a seasoned fresh water fish owner and have had 15+ fish for years in a 75 gallon tank and, I’ve bred angelfish, and had 4 tanks at once even…. and I have had very mixed results using fish medications. You’ll almost certainly want to separate the infected fish into his own “medical-quarantine-tank” (I often used a bucket). Using this method allows you to use less medication (it’s dosed out per gallon), avoids him getting the other fish sick, and avoids the medication hurting other fish unintentionally. In my experience though, if something is wrong with the swim bladder, that fish doesn’t have very high chances of survival. It’s worth mentioning, Goldfish are a very dirty fish. They produce a lot of ammonia, which is one of the biggest issues with freshwater aquariums (it can kill fish, spawn disease, makes your water cloudy, etc, etc). It very commonly increases when a tank is overfilled (I’ve even heard mention that gasping for air at the top of the tank is a symptom of heavy ammonia, though I personally suspect it’s just overcrowded tanks that have low oxygen, and also create heavy ammonia). To remedy this, try feeding them every other day, and sparingly. Goldfish are scavengers, so they’ll eat any food that’s fallen to the ground, even digging for it. They’ll eat some level of algae as well. It may be worth getting a filter insert that lowers ammonia (they’ll also be available at the store). Changing out 25–30% of the water on a weekly or bi-weekly basis will help a lot too.