Aquarium Polls

First Poll

What is your favorite brand of goldfish food?

TetraFin / Tetra
Other Brand

Current Results

Second Poll

What is your favorite type of goldfish?

Bubble Eye
Black Moor

Current Results

Goldfish Water

In order to keep goldfish happy and healthy, there are a few water-quality parameters that you must be aware of: water hardness, pH, and nitrogen . Before you place your goldfish in the aquarium, make sure to test the water.


goldfish bowl



The amount of dissolved mineral salts , namely calcium and magnesium, will determine the water's hardness. Water with high concentrations of salts is referred to as hard, while low levels would be indicative of soft water. Hardness is measured with the degrees of hardness scale (dH), which ranges from 0 to over 30 degrees, with 4 to 8 degrees reflecting soft water and 18 to 30 degrees reflecting hard water. This can also be expressed in parts per million- soft water is less than 75ppm and hard water is within 150ppm to 300ppm.

Goldfish prefer water hardness between 3 and 14 degrees of hardness. Eventhough goldfish can survive in water with a higher hardness, commercial kits are available at pet stores that will allow you to alter the water hardness, so there is no need to gamble with the health of your pet fish.




The amount of acidity in the water is referred to as pH. The pH scale ranges from 0 to 14 with a pH of 7 being neutral, a Ph of 1 being very acidic and a pH of 14 being very alkaline. This scale is logarithmic , meaning that each number is ten times stronger than the preceding number. For example, a pH of 2 is ten times more acidic than a pH of 3 and 10 times more acidic than a pH of 4.

The acidity of water, and hence its pH , is influenced by a variety of factors that include the amount of carbon dioxide and fish wastes in the water. In general, goldfish and koi are quite tolerant of various pH levels. Commercial pH test kits are very simple to use and available at most pet stores. This water parameter should be monitored every week or two to detect any changes. Whenever possible , the pH should be maintained between 6.8 and 8.0, and great fluctuatiions should be avoided. An abrupt drop in pH may be indicative of an increase in carbon dioxide or fish wastes. An increase in aeration or a partial water change may help to alleviate the problem.




Goldfish and koi , like all fish, are living creatures that obtain energy from food and burn that energy with the help of oxygen, which they breathe from the water. However, these processes generate waste products that are returned to the environment via the gills and the digestive system. These wastes are primarily carbon dioxide and nitrogenous compounds such as ammonia. In the aquarium, these wastes must be removed. Carbon dioxide generally leaves the water through aeration at the surface or through photosynthesis by aquarium plants. Toxic nitrogenous compounds are converted to less toxic compounds via the nitrogen cycle.

In nature, the nitrogen cycle involves the conversion of toxic nitrogenous wastes and ammonia into harmless products by bacterial colonies.

nitrogen cycle

In short, bacteria drive the nitrogen cycle as they convert solid wastes and other organic debris (uneaten food) into ammonia, ammonia into nitrite, and nitrite into nitrate. Nitrate is then used by plants as fertilizer and is removed from the water. A healthy aquarium depends greatly on the nitrogen cycle to reduce toxic ammonia into less toxic nitrogen compounds. When setting up a new aquarium, it is important to measure these compounds every week for the first couple of months. After this period, once a month is sufficient, unless you suspect a problem. You should see ammonia increase first, then decline as nitrite begins to elevate. As your bacteria colony flourishes, nitrite will decline as it is converted into nitrate, which increases slowly. Plants and frequent water changes will remove nitrate before it reaches toxic levels.

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There are 8 comments
Posted by JERRY B – USA

i'm new to the hobby but I' always loved fish tanks , besides the three betta's at about 3 yrs old (seperate of course) started with 1 white comet and 1 calico in a 14 gal tank , my? is wats better to keep on more the airation or the filter and how long for each? cause the filter kinda blows them around the tank?

Posted by suvasree – india

I love gold fish very much.i have two red oranda,two lion head,and two red cap gold fish in my fish tank. They are very pretty. I love the moment when they eat.and i start my every day with that beautiful moment. I have a photo of my first red oranda gold fish in my cell phone who died after five days of buying,because i kept it in a fish bowl.but now i am very happy because now i have a tank and my gold fishs are very happy there.

Posted by Jeri – New York


Aquarium water should never have any kind of smell if everything is working properly including the filter. Something is definitely wrong when you said your water has a bad smell. My suggestion is to buy an aquarium water test kit called "API Freshwater master test kit" and test the water in your aquarium tank. It's one of the more accurate test kit out there and will cost around $20-$30 . You can't really successfully raise fish without knowing what chemicals are present in the water so this kit will help you in that regard.

Posted by leanne – france

i have brought my daughter some fan tail goldfish and they all keep dying, the first fish died over night the first day we had it, i then went out and brought more fish along with a new tank, one died 48 hours after we brought it and another one has died now not even a week after we have brought them! I have got a filter, somewhere for fish to hide, plants and have put right amount of water cleaner in tank can anyone shed any light on what i am doing wrong? the water does smell quite bad, ive had goldfish before and havent ever bothered with a water filter or putting cleaning stuff in with fish and they have lived for years!!! im sure im not overfeeding fish (twice a day one flake each fish) they have a good sized tank with plenty of room to swim please can someone help as i dont want to see my daughter crying again and dont want to keep buying fish if im just going to kill them accidently

Posted by tiana – california

goldfish are awesome, but hard to keep.

Posted by nat – Saint Petersburg, FL

Plastic plants are completely ok and better to start with for beginners.

What I learned too from a good source is that if the water looks or smells funny or is not as clear as tap water when you put it in a clear glass next to tap water, then do a 20% water change adding the correct amount of both AguaSafe and EasyBalance by Tetra to the new water before adding it to the tank.

For these chemicals that neutralize the bad things for fish in tap water and get the water balanced in all respects for your fish, more is not better so read the directions and only add as much as is needed and no more. Sometimes with a small tank you will only need a few drops when you do a water change.

You do not need to measure or test anything or understand the complex nature of this cycle if that is not your ball of wax, so to speak.

Do this water change everyday until you see the water quality become clear and then just do it once a week.

Another great tid bit I learned is that you do not need gravel at the bottom of your aquarium! If you have a fishbowl then you do need it but goldfish should never be kept in fish bowls anyway. But gravel is only for looks and is messy and sand is even worse to clean. So if you are a beginner some large river stones found in aquarium stores work great for the bottom and to keep your plastic plants down on the floor of the aquarium and it is sooo much easier to clean. Wow!

But always remember the basic rules, no fishbowls, at least a 10 gallon tank to start with for even one goldfish to make them very happy, and a good air system for your tank to get the air bubbles flowing inside the tank as well as a good filtering system.

The more you learn the more you will know about the needs of your fish, but start off simple and then as you find out more you can get more into the hobby and get more complex.


Posted by chris – london

so do u need real plants or is plastic ok?

Posted by MaDDIE – Laguna Niguel

goldfish are awsweome thats y i have 18