Goldfish Care Sheet

Evan Baldonado

By Evan Baldonado
(Founder of AquariumKids)

Reading this care sheet may take you 10 minutes, but it just may save your goldfish's life!

Why am I writing this?

Last year, I won my goldfish at the annual Duveneck Harvest Carnival. This year, I hope that more goldfish will survive and become beloved pets because of this care sheet.

Small goldfish by ぱたごん (CC 3.0)
Two small goldfish
[Image by ぱたごん - CC 3.0]


Goldfish care can be divided into four main sections—if your goldfish has adequate space, good water, shelter, and good food, everything else should take care of itself.

Choosing a Tank

After bringing your goldfish home, you will first need to find a place for it to live. As Goldfish can grow 12+ inches and produce massive amounts of waste, the traditional goldfish bowl simply isn't adequate. Not only do bowls stunt goldfish growth, but they also allow for toxins to accumulate incredibly fast which can be quite dangerous to your goldfish. A typical full-grown goldfish needs at least 25 gallons of water. As pointed out by @ParadoxFish on Instagram, a 20-gallon tank may seem close to a 25, despite actually being 20% smaller. Look for a tank of at least 25-30 gallons for your goldfish, possibly even larger. Certain larger varieties of goldfish may grow even bigger and require more space. Most likely, though, your goldfish is not full-grown and is less than 4 inches long. To know what size aquarium your goldfish currently needs, follow the chart below:

Goldfish Size (Inches) Aquarium Volume (Gallons)
<1 3+
1-2.5 5+
2.5-4 10+
4-6 15+
6-7 25+
7-9 30+
Your typical goldfish won't need more than a 25 - 30-gallon aquarium.
9-12 40+
12-16 55+ or Pond
16-20 75+ or Pond
20-24 100+ or Pond

Note that this table is only applicable for the first goldfish. Each additional goldfish requires an additional 3/5 of the volume of the number of gallons recommended above. Remember, goldfish are always happier in larger tanks—these are minimum requirements. You may want to consider buying a larger aquarium from the get-go to avoid constant upgrades.

Acclimating your goldfish

Now that you have your aquarium, it is time to fill it up with water. You can just use plain 70±5F tap water. Once your aquarium is full, add your dechlorinator as specified to remove toxic chlorines and chloramines. Personally, I use Prime by Seachem because it detoxifies heavy metals (which can be potentially dangerous), ammonia, nitrite, and nitrate as well as chlorine/chloramine. Don't worry if you don't have a water conditioner yet – you just use bottled water.

Once you are done filling up your tank, float your goldfish bag in the aquarium. The method of acclimation that I am going to cover here is the float-acclimation method. Open the top of the bag, not allowing any water in. Every 5 minutes, add about 1/4 cup of aquarium water to the bag. Repeat this for 30 minutes. If the bag fills before 30 minutes is up, wait for the remaining minutes. When you are done, dump the goldfish and the water in the bag into the aquarium if there are no goldfish already in the aquarium. If there is already a goldfish in the aquarium, gently net your goldfish and place it in the aquarium. Dispose of the bag afterward. Edit: The Drip-Acclimation is better for fish than the float acclimation method, but requires a way to slowly drip tank water into the new water. You can read more about it here. Now you have a goldfish and an aquarium, and we have already talked about two of the things goldfish need not just to survive, but thrive!

Substrate, Plants, and Decorations

The third thing goldfish need is shelter. This one is a bit more complicated to write than the aforementioned part of this paper, because everyone has their own tastes. You might be happy with a oyster bubbler ornament and a few fake plants, or you might prefer a densely planted, aquascaped aquarium with multiple driftwood and rock pieces. Let's start with the bottom of the tank, substrate. Pea-sized gravel is not a good choice because goldfish naturally sift though substrate in their natural habitat, and may choke on it. Because we can't use pea-sized gravel, we have two more choices left: specialized aquarium sand and large (1-1.5 inches) river rocks. Both have their own pros and cons, so feel free to choose whichever you fancy. Moving away from the bottom of the aquarium, we have plants and decorations. When choosing live plants, remember that goldfish naturally pick at plants, so you will want to pick hardy and/or fast growing plants, or you heighten the risk of losing your plants. Some good varieties include: Elodea/Anacharis, Amazon Sword Plants, and Bacopa. Once you have bought your live plants, remember to quarantine them in an empty jar for 1-2 weeks (even if they advertise themselves as being pest and disease free). If you don't want live plants, another option is faux, or fake plants. Fake plants are good because they require no maintenance except for cleaning algae off occasionally. However, fake plants lack one of the best qualities of live plants- they don't clean and purify the water.

Once you have your plants (live or fake), you can choose some decorations for hiding places. Regular plastic ones are great because they provide hiding spots for your goldfish and don't change the pH of the water like driftwood does. When you are choosing decorations, don't get any ones with sharp edges, or ones that are rough because your goldfish could hurt itself on them. Remember, goldfish will always feel more comfortable and less stressed (which makes your goldfish less prone to disease) in a natural looking environment.

Feeding Time

There are lots of options when it comes to goldfish food: flake, wafer, pellet, live, freeze-dried, homemade, aquatic plant, gelatin, frozen, and stick. The best thing that you can do for your goldfish is to give it a wide variety of food. A good diet would be about 2/3 plant matter, and 1/3 animal matter because goldfish are naturally mainly plant-eaters, who occasionally snap up some bugs. Food high in carbohydrates is also especially good for goldfish. One of my goldfish's favorite treats is Hikari Tropical Micro Pellets. I highly recommend it for someone who wants a high-quality, balanced plant/animal-matter food. Do not feed your goldfish bread—it expands when it soaks in water, and may cause your goldfish to have stomach problems or problems swimming.

Types of Goldfish

As a result of selective breeding, there are many different types of goldfish available today. Most goldfish fall into one of two categories: regular or fancy. The sleek, regular fish consist of Comets, Commons, and Shubunkins. There are many more varieties of fancy goldfish (Orandas, Moors, Ryukins, Lionheads, and Telescope eyes to name a few) than regular ones.

If you have a choice, I would recommend that you choose regular-type goldfish because many fancies have internal organ problems as a result of their deformed shapes. However, if you already have a fancy goldfish, you can be happy that they won't grow as large as regular types and they won't need as big of an aquarium when they are adults. When choosing multiple goldfish, don't get a mix of fancies and regulars, as the regulars will outcompete the fancies for food.

Regular Fancy
Size: Generally larger Generally smaller
Activity level: Faster & more active Slower & less active
Tank size: Needs larger tanks Okay in slightly smaller tanks
Health problems: Generally healthy Some are prone to internal organ problems
Tank mates: Keep alone or with other regulars Keep alone or with other fancies

Water Changes

The two most common mistakes that people make while doing water changes are: not using the correct-temperature dechlorinated water and removing the goldfish from the aquarium to do a 100% water change. For doing water changes, get a siphon to remove the water from the aquarium. I siphon my water into plastic Sterilite® bins. Remove about 40% of the aquarium water, while keeping the goldfish IN the aquarium because 40% of the water leaves enough beneficial bacteria in the water and the pH of the new water may be different from the old water. In addition, your goldfish will be much less stressed if you leave it in the tank rather than taking it out. You should do water changes every one to two weeks unless your tank is fish-in cycling or one or more of the water parameters is out of whack.

The Nitrogen Cycle

The nitrogen cycle goes by multiple names: biological cycle, startup cycle, and a few others. Every new aquarium will go through the nitrogen cycle, either fish-in or fishless. I think that fishless is more humane, as fish will inevitably have toxins in their water with a fish-in cycle. If you are a beginner, and you don't already have your goldfish, please consider a fishless cycle, as only more experienced aquarists can keep the amount of toxins at a minimum while still cycling the aquarium. If you already have the goldfish, make sure you test your water parameters (ammonia, nitrites, nitrates) daily, while cycling. The nitrogen cycle starts as soon as you place your goldfish or some other ammonia source in the aquarium and lasts for around 1-2 months. Goldfish waste decays and produces ammonia or ammonium (depending on your water's pH), both of which are toxic to all fish. If your pH is less than 7, your goldfish waste will convert into the much less toxic ammonium. On the contrary, if your water's pH is above 7, it will become ammonia, the more toxic form. After awhile, bacteria will start to build up which remove the ammonia/ammonium. The cycle isn't done yet- the bacteria's waste product is nitrites, another toxin. Wait a few more weeks, and you will begin to get nitrate readings, the waste product of another type of bacteria which eats nitrites and excretes nitrate. Nitrate isn't nearly as harmful to fish as its cousins, but is still harmful to fish at levels over 25ppm. It can be removed from the aquarium by water changes and plants. Even though plants remove nitrates and small amounts of ammonia, you still have to do water changes because goldfish don't like old water, trace minerals will be depleted, and some types of organic wastes will build up. Having plants, better filters, and a smaller bioload will reduce the time between water changes, but you will still eventually have to do them.

Male goldfish by Blubbi321 (CC 4.0)
A male goldfish with tubercles
[Image by Blubbi321 - CC 4.0]

Breeding Goldfish

When you see all of the feeder goldfish at the store, you may think that goldfish are easy to breed. Whatever the case, you probably don't really want hundreds, or even thousands, of baby goldfish to take care of, so I won't cover breeding goldfish in this article.


For information regarding goldfish diseases, I have found that is a good site.

Aquarium Equipment

There are may different types of aquarium equipment: aerators/bubblers/airstones, heaters, chillers, UV sterilizers, CO2 reactors, lights, filters, and automatic feeders. With the exception of filters and maybe aerators, your goldfish can easily survive without the other aquarium equipment. However, your goldfish will be healthier if its temperature it maintained between 65 and 75 degrees Fahrenheit with a heater and a chiller. My goldfish's aquarium has (from the list above): an aerator, a chiller, lighting, and a filter.

Aerators make sure that your goldfish always has enough air to breath and give your goldfish stimuli. Heaters and chillers are pretty self-explanatory. UV Sterilizers kill free-floating harmful bacteria. If you have many plants, you may want to consider a CO2 reactor. CO2 reactors inject CO2 into the water, allowing for faster plant growth when used along with lighting and fertilizer. The one downside of them is that they reduce the pH of water. Goldfish prefer a pH between 6.5 and 7.5, so my aquarium doesn't have one because Palo Altan water already has a low pH of 6.5. If you bought an aquarium kit, you probably already have lights and a filter. If not, at least consider getting a filter to provide a growing medium for ammonia-removing bacteria.

Are you the kind of person who takes lots of vacations? When you are gone for more than three days, your goldfish will need to be fed. Preferably, someone will come over to feed them for you, but if that isn't possible try looking into an automatic feeder. Their only downside is that it is possible for them to malfunction, dumping all of the food at once or no food at all for weeks.

Final Tips


This article was written by Evan Baldonado (a 7th grader at the time) and published 9/24/13. You can email him for any reason at evanb [at] aquariumkids [dot] com.