Goldfish 101: Everything You Didn’t Know about Our Favorite Aquatic Pets

Go Fish!

You want a pet, but your apartment building doesn’t allow dogs or cats. Or maybe your gradeschooler was a lucky winner at the school carnival, and suddenly there’s a live prize in a water-filled plastic bag next to you in the passenger seat. Maybe you just love fish. You are thinking about trying your hand at fishkeeping. Whether you’ve kept pet fish before or are a complete novice, with goldfish in your future, there can be a lot more to learn than you might think. If you’re just home from the pet store, or even if you’re staring dumbfounded at that little fellow in the plastic bag, vaguely aware that he has only so much oxygen, cursing the school, relinquishing your plans for the day and telling yourself not to panic, don’t worry. PugetPets has the basics to help you keep your head above water!

The Truth about Tank Size

Whether you’re a conscientious parent left “holding the bag” or are making a deliberate foray into fishkeeping, the most important thing you will have to consider before committing to caring for goldfish is tank size. A common myth persists that goldfish can live happily in small containers, even in pretty glass bowls. It is also frequently asserted that goldfish “grow to the size of their tank.” While not completely false, this is a somewhat misleading statement. Similar to the way the growth of human children can be stunted by adverse conditions, pet goldfish frequently suffer from stunted growth, an unhealthy condition caused by a variety of factors that often result from inadequate space. These factors include increased toxins in the water, acidic water, low oxygen levels, production of a variety of stress hormones such as cortisol, and lack of physical fitness. Goldfish provided with a natural, healthy environment and sufficient space will grow to the natural size appropriate to their species. What most pet stores don’t tell you and many of us don’t know is that the goldfish for sale in their tanks are baby fish. An aquarium suitable for a baby will not be big enough for long. Starting with a tank appropriate to the size your fish will be when they are full-grown adults is one of the best ways to ensure their physical and emotional health and longevity.

So how much tank space does a goldfish really need? A “fancy” (split-tailed) goldfish naturally grows to be six to eight inches long. A “common” (single- or straight-tailed) goldfish can grow to be a foot long! While recommended tank sizes vary somewhat depending on the source, the “goldfish golden rule” is generally considered to be five gallons of water per inch of fish. In addition to volume, tank dimensions are also important, as fish need room to maneuver. According to The Goldfish Tank, fancy varieties should have a tank three feet long and with a volume of at least 20 gallons for one fish, with an extra ten gallons for each additional fish. Common varieties will need a four-foot long tank with a volume of at least 30 gallons, with an extra 12 gallons for each additional fish.

This seems like a lot, but don’t drop that baggie just yet! Having a larger tank, while costing more initially, can be extremely rewarding down the line. Losing unhealthy goldfish to shortened life spans can be especially hard on kids. A suitable tank can help you avoid a succession of back-yard burials and replacement pets. Raising healthy fish with normal life spans will allow you and your family to watch your fish grow into large, healthy, bright and showy individuals. Plus, you will have to perform fewer water changes than you would if your fish were in a smaller tank. Happy, healthy fish (and kids!) and a lower maintenance requirement are great advantages of having a large tank. Goldfish have a natural lifespan of up to 10 or even 20 years, so by providing proper care, including a spacious home, you’ll get lots of time to enjoy your finned family members!

Tank Enrichment

Studies have shown that fish respond positively to an enriched environment but show signs of despondency in a barren environment. Like all animals, they are happiest when engaging in their natural behaviors. Foremost, provide your tank bottom with a large-grained gravel. Goldfish love to suction up gravel and spit it out again, looking for food. A large-grained type will prevent the gravel from getting caught in your fish’s throat. Use fish-friendly tank decorations. A central structure where the fish can hide, with plenty of maneuvering space around it works best. Goldfish are not the most agile of swimmers, and this way they can have lots of room for exercise. Make sure the decorative structure isn’t hollow, as these structures can harbor harmful bacteria. Steer clear of structures that have sharp edges that could cut your fish. Plastic plants are recommended, as goldies are notoriously voracious omnivores, who will strip live plants in a day, resulting in overfeeding and, of course, no more plants. Some fish keepers have floated live water-loving tropical houseplants, such as philodendron, in their tanks. The plants thrive on the nutrient-rich water and grow roots into the fish’s environment, but the fish will not eat them.

Water Quality

Ensuring good water quality for your fish is paramount. Clean your tank and gravel with fresh water (no soap!), even if they are new. Fill your tank with tap water or distilled water and add water conditioner/dechlorinator according to the instructions. Untreated tap water contains chlorine and other chemicals and minerals that will kill your fish! Set up a water filter. Goldfish produce large amounts of waste, and they must have a water filtration system. Hardy fish, they can tolerate a wide rang of temperatures. Their extreme limits are roughly 55 to 75 degrees Fahrenheit. You do not need to have an aquarium thermometer for these fish, unless you’d like to. Room temperature is a good general rule to follow. Gradual, seasonal temperature changes are fine, but your fish can be dangerously stressed by sudden, dramatic changes, so take care when re-introducing them after a water change. Whenever possible, make sure your tank is ready for your fish when you bring them home. To ease the stress of temperature change, float their transport bag in their aquarium water for a few minutes before releasing them to their new homes.

Fish tanks require regular cleaning. Partial water changes, in which a large portion of the tank water is replaced with fresh, dechlorinated water, will be necessary. Even if the water does not look dirty, it still contains a build-up of harmful toxins that must be removed by changing out the water. Less frequently, a complete water change will be in order. See for a great, easy-to-follow tutorial on how to clean your tank. You can also keep a bottom feeder fish to help keep excess algae out of your tank. Make sure you get a type that is appropriate to be housed with goldfish.

Light Cycle

Like us, goldfish are diurnal, meaning they are awake during the day. While they have no eyelids and never really stop swimming, they do sleep. They will slow down and often just sort of “hang out” at the bottom of the tank. Your fish appreciate a regular light-dark cycle just as you and I do. Avoid keeping their tank in direct sunlight, however, as this will encourage too much algae growth and could raise the water temperature, causing dangerously low oxygen levels.

Feeding Your Goldfish

The kid in all of us loves to watch our fish feed. However, overfeeding is very dangerous. It is said that more goldfish die of overfeeding than of anything else. Feed your fish twice daily at regular times and in the same place in the tank. Do not give them more food than they can eat in one minute. Remove any excess food. Skip a couple of non-consecutive feeding days a week, as a little fasting is actually good for your fish. The best type of food for goldfish is sinking pellet food, because they enjoy rooting around in the gravel for their food. This regular diet should be supplemented. They love a variety of live foods, which you can purchase from your fish store. Freeze-dried foods, such as blood worms, are also a favorite special snack. Always moisten the freeze-dried food in a bit of aquarium water before feeding it to your fish, since it will expand and can cause stomach problems if not pre-wetted. These omnivores also like their veggies. Bits of peas, broccoli and cucumber are all foods that are great for supplementing your fish’s diet. Goldies have even been known to snag a hapless housefly now and then. If you see this happen, it’s probably a good idea to enforce a post-fly fast day for your full-bellied fish!

Choosing A Healthy Goldfish

So, you’ve decided to take the plunge! If you aren’t the lucky parent of a carnival goldfish winner, pay careful attention to selecting your fish. If possible, purchase your fish from a reputable aquarium store rather than from a pet store. These are more specialized stores with highly trained staff and facilities capable of providing healthy environments for the fish in their care. Look for robust individuals who are swimming upright in a leisurely manner. Avoid fish that are swimming on their sides or darting around quickly, as these can be signs of problems with a fish’s swim bladder (a special organ that regulates a fish’s buoyancy) or of parasites. White spots all over the fish’s body indicate a common parasitic fungus called ich. Ich is very contagious to other fish and plants, so you should not select any fish from a tank with an infected fish. Avoid fish with splitting or torn-looking fins or those who appear despondent or seem to be gasping for air at the surface. Seeing any of these problems should raise a red flag that you might want to buy your fish elsewhere.

Goldfish are “loose shoalers” by nature. In other words, they don’t form tight schools like sardines or herring, but they do seek the company of others of their kind, often when they are nervous or not feeling well. You can observe this behavior most dramatically during water-change times. They are tactile fish and seem to enjoy some physical contact with other fish. For this reason, choosing two or three goldfish is the ideal. With a “big pond” and a little TLC, your fish will adapt to their new home swimmingly! PugetPets is available to feed and monitor your fish while you’re away and wishes you many years of fun and fascination with your finned friends.