Many people have had a goldfish or two in their lives, only for the small fish to die for no apparent reason. The main problem is that there are a lot of misconceptions going around about how to care for these fish. People who think they are doing it right are actually doing everything wrong. Learning how to care for your goldfish tank now will ensure all your fish a long and healthy life.
Goldfish and other livebearer fish’s are a cold-water species, so it is true that they don’t need, and actually do better, without a heater. This is about the only piece of conventional advice concerning the keeping of these fish that is true. Some things you need to know are: a bowl is a horrible way to keep them, they absolutely do need a filter, and they will not stay as small as the aquarium they are placed in (they will just die instead, due to lack of enough water and too much waste).
A proper aquarium for goldfish is at least 10 gallons. And even at this size, only three to four fish can be kept. They will quickly outgrow this aquarium, but some people solve this problem by trading in their large fish for new smaller ones every few months at the pet store. Since larger fish are worth more money than smaller ones, many pet stores are happy to do this. No fish bigger than 3 inches should be kept in a 10 gallon aquarium.
An adult goldfish is between 6 and 12 inches long, depending on the type. It needs at least 10-20 gallons of water per fish. Strong filtration is necessary in order to keep them healthy, as these fish produce a lot of waste. Regular water changes of 10-30% every week or two are necessary.
Filtration in an aquarium is partially mechanical (large pieces of waste are trapped) but also partly biological. This is where good (beneficial) bacteria are used to turn the fish waste into a nontoxic byproduct.
Overfeeding is one of the most common causes of fish death in home aquariums. Your fish should be fed a flake food that is specially formulated for goldfish (not tropical fish) and only fed what they can eat in one or two minutes, once a day. Excess amounts of food will dirty the water, or the fish will eat it and get fat. Fat fish do not live as long as healthier, leaner ones.
There are no conventional aquarium fish that can share living space with goldfish without compromising the health of at least one of the species, so these fish should be maintained only with their own kind. Fancy types of various varieties can be kept together, but should be kept separately from the faster, stronger standard type that can out-compete them for food and bully the weaker fish.
Given the proper aquarium setup, this is a hardy species of fish. If you maintain your tank with regular water changes, feed properly, and find new homes for fish that have outgrown any smaller tanks that you keep them in, your pets might live up to their maximum lifespan of 20 years.