How to Care for a Zebra Danio
To care for zebra danios, start by setting up a tank that's at least 10 gallons so they have plenty of space to move around. Next, use test strips to test the water for chemicals and pH levels, and treat it with a water conditioner if necessary. After you introduce the danios to the tank, feed them a variety of food, such as fish flakes, brine shrimp, and blood worms. Once a week, use a scraper to remove algae from the tank and replace 10 percent of the water with fresh water to keep the tank clean.
Purchase a ten-gallon tank or larger. Danios are social animals and need space for themselves and their friends. The tank should come equipped with an exterior power filter, a bio-wheel, and an aquarium heater. Because they are hearty, it is generally possible to keep danios without a heater. However, a heater is good for maintaining optimal conditions, especially if you plan to breed the danios. You might be required to assemble the tank. If so, follow the instructions on the box. Purchase chemicals for water treatment. Local water companies will usually use some chemicals, like chlorine, that can be harmful to your fish. At the pet store purchase some testing kits to determine if the water is safe. You will probably want a sodium thiosulfate solution to treat chlorine and Amquel to treat chloramine. To get more information about the chemicals in your water supply, ask the local pet store owner or call the water utility directly. Add gravel to the tank. Fish like a layer of gravel at the bottom of the tank. Keep approximately 1/4th of an inch of gravel in the tank. Pour water into the tank. Simple tap water is generally good for your fish, though you will need to treat it. Fill the water nearly, though not all the way to the top of the tank. It is necessary to keep a layer of oxygen at the top of the tank. Treat water. In addition to adding sodium thiosulfate and Amquel to the tank, treat the tank for pH levels. There are a variety of acids and bases that can be purchased at the pet store to adjust the pH level in your tank. Test the level and adjust the pH until it is in the 6-8 range, preferably 7. Get a group of 6 or more danios. Danios are social animals that like to be in the company of other fish. A group of 6 or more is optimal. Danios get along with some other varieties of fish as well, including corydoras and tetras. Get danios of different sexes. If you want to breed your fish, you should be sure to get some danios of different sexes. To distinguish between the two, remember that males have yellow stripes and females are generally larger. Danios breed rapidly when left to their own devices. However, they will often eat many of their fry. Move fish to their tank as quickly as possible. Even the mighty little Zebra Danio cannot survive longer than 8 hours in the bag that the pet store provides. When you transfer the fish to the tank, do not transfer the water they came in with them. It will have too much ammonium. Feed the danio. Danios enjoy a variety of food sources. Commercial produced flakes will usually suffice. You can also feed them blood worms, daphnia, and brine shrimp. Maintain tank temperature. Danios are hearty and are comfortable in temperatures from 65 to 75 Fahrenheit. You can often maintain this temperature without a heater, but a heater will help. A slightly higher temperature, 78 Fahrenheit, is optimal for encouraging breeding. Clean the tank weekly. When you clean the tank, you do not need to remove all of the gravel, however, you should use a siphon to suck up the waste that accumulates on the bottom of the tank. Use a scrapper to remove algae from the glass on the tank. After finishing these tasks, remove and replace 10-15% of the water. Do not remove fish when changing the water, this will cause unnecessary stress. When replacing the water, put new water into a bucket that is exclusively used for this purpose (If you use it for household tasks it might accumulate dangerous chemicals). Test and treat the water as discussed previously. Use a siphon to slowly introduce the new water back into the tank. 
Purchase a ten-gallon tank or larger. Purchase chemicals for water treatment. Add gravel to the tank. Pour water into the tank. Treat water. Get a group of 6 or more danios. Get danios of different sexes. Move fish to their tank as quickly as possible. Feed the danio. Maintain tank temperature. Clean the tank weekly. 