Vet Q & AFirst fish tank: What Tetras and supplies for my 12-inch tank?
Before you buy any fish, you will need to set up the tank. A basic set up includes: a tank, filter, hood/light, heater, gravel and some decor. The tank should run without fish for at least 4 to 6 weeks. This gives it time to cycle. The Nitrogen Cycle is critical to the health of the tank and any fish you will be keeping. During this time, beneficial bacterial will populate the filter and substrate (gravel). These bacteria will be responsible for breaking down fish wastes and other wastes (uneaten food, dead plants, etc.). You will need a home test kit to monitor water chemistry (ammonia, nitrites, nitrates, pH) or you will have to submit water samples for testing. Most pet stores will do this for free or for a small fee. At first, you will see high levels of ammonia and nitrites. Over time, as bacteria grow, these levels will drop. When ammonia and nitrites are at 0 ppm and nitrates are below 20 ppm, you can consider adding fish. Regular (every 1 or 2 weeks) partial water changes as well as filter changes will be needed to maintain stable water chemistry and adequate water quality.
The size of your tank will determine what fish and how many you will be able to keep. Most Tetras do best in groups, so a 12 inch tank may not be large enough.
There are several article in the Petco Pet Education Center, formerly Petcoach Library that will provide more detailed information. Click on "Educational Center" at the top of the page, then scroll down to "Articles" and click. Use the Search Bar to find articles regarding aquarium set up and fish keeping.
Updated on September 24th, 2025
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