Guide: Setting up a Goldfish Tank

Tank Size:

Make sure to choose an adequate tank size for the goldfish you wish to keep. Many species of goldfish grow to be quite large, so a small bowl or small tank is not a good option for these fish. Comet Goldfish often grow in excess of 35-40cm and fancy goldfish such as Oranda Goldfish, Pearlscale Goldfish, Black Moor Goldfish, etc. grow 16-25cm in length. Due to the large future sizes of these fish, it is good to start with a tank size that is at least 110-115 liters in volume.



Substrate color is based on personal preference, but we recommend a dark to bright colored substrate to help hide dark waste buildup that can occur in a goldfish tank. Substrate size should be medium to large sized and the common “pea sized” 2-3 mm sized gravel most commonly found may not be ideal for the goldfish aquarium as larger goldfish may swallow this size substrate.



Goldfish Aquarium décor is also your personal preference, but make sure that you use décor that has smooth surfaces and can not scratch or damage the sides of your goldfish. This will be especially important as your goldfish start to grow to their larger sizes.



For a goldfish system, any style filter will work great, however you will want to make sure that you have good water turnover (typically we recommend double the liter per hour rating of the aquarium size you have). In addition you will want to have enough space for biological media such as Seachem Matrix because this will help to provide housing to the beneficial bacteria that is necessary to keep the tank clean and free of organic waste in the form of ammonia, nitrite or nitrate. Also, we recommend the use of good chemical filtration and MatrixCarbon and Purigen are fantastic options to clean and polish the water.



Cycling is the process of building enough “good” bacteria to handle removing all the organic waste from the system when you have a fully stocked aquarium. To cycle it is best to use a very sturdy bacterial additive, like Seachem Stability to provide the right types of bacteria to handle the fully stocked system. In addition to adding bacteria, you will also need to add a food source to produce ammonia for these bacteria to encourage growth and colonization. You can do this by adding fish, pure ammonia or even fish food to the tank to feed the bacteria. Ammonia will typically need to peak between 1-2 ppm to facilitate the cycle. Pro tip: Prime detoxifies ammonia so it is not harmful to fish, but leaves it in a form that the bacteria can use as food. You can use Prime every 48 hours to keep your ammonia and nitrite bound in a nontoxic form until your tank is fully cycled.

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