Goldfish Care Guide

By Dr Eloise Bright 9 Min Read

Goldfish are as popular as they are beautiful. With proper care and housing, some of these colourful fish can live for 20 years or more.

Goldfish and a similar fish known as “koi” have been kept as ornamental pets for more than a thousand years. Koi and goldfish have shows and societies devoted to them, just as there are shows and societies for dogs, cats, and fancy mice. Although goldfish are associated with fish bowls, these bowls were never intended to house the animal for extended periods. In fact, they were originally used to show off exceptional fish during dinner parties and other showings, and then the fish would be released back into the pond.

Quite possibly the most important factor for keeping your pet healthy is the choice of accommodations. Proper housing for these animals includes ornamental fish ponds and large aquarium tanks. Even though they are considered a coldwater fish, goldfish tolerate the range of normal Australian temperatures pretty well so long as there is enough water available. The higher the temperature of the water, the less dissolved oxygen it contains. Therefore, the warmer the weather is likely to be, the bigger the tank needs to be, to prevent suffocation. For most of New South Wales, a good rule of thumb for minimum tank size is 25-30 gallons for the first fish, and 10-15 gallons per additional fish. A small school of three to five fish is a good place to start.

It’s also very important to keep any fish tank out of direct sunlight. It’s amazing how fast the sunshine can heat up the water, no matter what the air temperature might be.

Now you know why so many pet goldfish die after just a week or two in a goldfish bowl.


The bare essentials for goldfish are a tank and canopy of appropriate size, clean water, gravel or glass pebbles, a heavy-duty filtration system, fish food, and some live or silk plants for the fish to hide in. Other useful items are a fish net, a couple of clean buckets which have never contained anything but water (no soap, ever!), an algae scraper to clean the walls of the tank, and a siphon for cleaning the gravel.


Left to their own devices, your fish will get enough exercise simply swimming around attending to their fishy activities. The slim breeds are much more active than the rounder, long-finned varieties.


Feeding a goldfish is a simple matter. There are many excellent commercial goldfish foods on the market. The small pellets and flakes are the best choice, even for large fish. These allow all of the fish to grab something to eat, even if one of the fish is a bit of a bully, which happens sometimes. The large pellets are for ponds containing large schools of fish.

The usual advice is to feed fish two or three times a day, only as much as they eat in two minutes. Another way to estimate is to give the amount of food that would cover each fish’s eye. A missed day or two, from time to time, will not hurt them.

One of the most common causes of premature death in goldfish, other than suffocation, is the fish equivalent of constipation. Fortunately, this is easy to prevent. A few times a week, blanch a small piece of spinach in hot water, and float it in the fish tank. The fish will nibble on it, and it keeps them “regular”, to borrow the Americanism. Sometimes, this can save the life of a goldfish that is already in difficulty, but it is much easier to prevent the problem than to solve it.*


A good heavy-duty filter will do most of the heavy lifting for you. The types which hang on the back of the tank and produce a waterfall effect are simple and effective. They are usually labeled according to the quantity of water they are meant to treat. If your tank holds 60 gallons of water, for example, choose one with a range of 60-80 or 65-90 or something of that sort. Avoid one where the top of the range is the size of your tank. A filter meant for 40-60 gallon range will not keep a goldfish tank clean enough, especially in temperatures over 74F/24C.

Replace roughly a quarter of the water each week, using the siphon to remove water from the bottom of the tank. This will double as a “vacuum cleaner” to pull debris off of the gravel. Pour in water that has been sitting at room temperature for at least 24 hours. The sitting allows the water to stabilize its temperature. It allows the chlorine and similar chemicals which are often found in tap-water to evaporate. Chlorine isn’t any better for a fish’s gills than it is for your lungs.

The bright green algae that often grow on the walls of the tank are harmless. If you don’t like the look of the stuff, simply scrape it off with the algae scraper. You’ll see little sheets or films of algae forming while you scrape. Usually, these will be gobbled up by the fish.


A canopied goldfish tank is appropriate for any home except for one in which many airborne chemicals are used: chemistry experiments and some air fresheners can poison the fish. When choosing a tank, remember that water is heavy. If the aquarium will be placed on an upper floor, or if you live in a high-rise building, find out whether the floor can withstand the weight of the tank, the water, the stand, and the gravel before you come home to several dead fish, water-damage, broken floor-boards, and perhaps a hole in the ceiling of the room below.


There is rarely any training needed for a goldfish. Some of them will learn to “mouth” at a safe item held near the water surface, and most of them will come to the front of the tank to greet you once they have settled in.


Are goldfish right for you? Do you have room for a large fish tank and a floor that can handle the weight? If you have decided on these brightly-coloured coldwater critters, the next step is to set up a tank and let it settle for a week or two. While it is settling, hop onto a few goldfish fanciers’ forums online and check out the local pond and aquarium shops to choose which fish you want.

*This treatment is a common remedy used by pond keepers and aquarists in Nova Scotia, Canada. It does not seem to be well-known elsewhere, although strained peas are often suggested for the same purpose.

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Dr Eloise is a Clinical Lead at Love That Pet and one of our resident pet care experts. She also curates the select range of vet recommended and approved products which feature on our site.
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