If you are going to buy goldfish for your aquarium, there are several things to consider before making a purchase.
The first consideration is if you have the appropriate housing for your new pet goldfish. Do you have a big enough tank? Or if you plan to put him in an existing tank is there enough room? Each goldfish needs about 7 gallons of water to himself and overcrowding a tank to get more fish to “look at” will only cause disease and death for your finned friends. If you are serious about keeping goldfish, one recommendation is to buy a tank specifically for them. I would say you would want a 30 gallon minimum in order to have 5 or 6 healthy goldfish.
Before you buy your new goldfish, make sure his tank has the appropriate climate.
Goldfish need cooler water temperatures (around 68 degrees F) than most other tropical fish. Don’t even try to put him in a tank that is above 72 degrees F as it will make him sick and drastically shorten his lifespan. If you will be keeping the fancy long tailed kind of goldfish, make sure your filtration system does not create too much of a current. If you are putting him in a new tank, don’t even think about buying a goldfish until the tank has cycled.
Finally, if you plant to put your goldfish in a community tank, make sure he is compatible with the other fish already in the tank. The deep bodied goldfish like moors, orandas and veiltails should be kept in a tank by themselves. Ask your pet store owner or fish specialist which species you can mix and match when you go to buy your fish.
Your goldfish should be bought from a reputable fish store.
Pick one that is well stocked and looks well cared for inside. Go in ahead of time and ask some questions to see how knowledgeable they are. If you stick with a store that has pride in it’s work you can be pretty sure you can trust them to give you good advice and sell you healthy goldfish.
When you finally go to the store to make your purchase, make sure you buy a healthy looking goldfish. Look at the other fish in the tank to try to determine if there is any disease in the tank. If other fish show signs of disease, the particular goldfish you are buying may not show any symptoms yet but could get sick soon after you bring him home and infect your other fish!
Finally, make sure you get a guarantee. Any reputable fish shop will give you a warranty of at least 3 days on a goldfish. If your goldfish dies within 3 days it is usually not your fault so they will replace him with another fish (they may request a sample of water so they can test it). It’s not really the cost of the fish that is the issue, it is the sincerity and honesty of the shop. The guarantee simply shows you that their intentions are good.