(Source: M. Westerfield from Zebrafish Book 5th Edition)
Zebrafish are available at pet stores throughout the world. They can be most easily maintained in 10 gallon (45 liter) aquaria heated to 28.5°C (above 31°C and below 25°C, zebrafish probably won't breed and development will be abnormal) with 25 fish per tank. If you replace 1/3 of the water each day by siphoning up debris from the bottom of the tank, a separate tank filtering system will not be necessary. Otherwise, use a filter and replace about half the water at least once a week. Tap water, aged a day or more in an open (heated) tank to release chlorine, is adequate although more consistent conditions may be obtained by adding commercial sea salts to deionized or distilled water (60 mg of Instant Ocean® per liter of water, for example). Adults should be fed 1-2 times per day with a variety of food (see Food). It is a good idea to clean the tank by siphoning after the second feeding.