# Freshwater Aquariums > New To the Hobby ? >  How To Choose Tropical Fish and Keep them Healthy

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Tropical fish are the fresh and salt water fishes found in tropical environments around the world. They are often called aquarium fishes because fish keepers often prefer tropical fish due to their vibrant colors. 
Tropical fish are warm water fishes. Monitor the temperature of your aquarium's water using a heater and thermometer. As a universal rule, your heater will require for one Watt of power for each liter of water in your tank. Set it to the appropriate temperature. To maintain collectively, it is best to opt for species that thrive in the same temperature of water.
Research about the species of fish you want to keep. Even if it is individually or collectively, you should know about the species before buying them especially if you are to keep them together. The fish should be both compatible with each other with regards to preference of water and competition. It is best that you know which two or three (or more) species go together.
Make sure your tank is ready before you buy the fish, or before it gets delivered to you. The tank should have the right temperature, the correct amount of water, and that the water quality must be viable for your fish. Have a test kit on hand because this will smooth the progress of determining if your tank water is just right.
Wait for a little while before releasing the fish to the tank. Keep the bag the fish came in, afloat for 15 to 20 minutes. This will allow your new tropical fish to get used to the changes in the water temperature. Then add a small amount of tank water in the bag and let it float for an extra five minutes. This procedure is repeated two or three times to facilitate the equalization of the pH of the water the fish have been packaged in with the tank's water.
Always be on the lookout out for your fish. Ensure that they are not violent toward each other and that none of your new tropical fish are ill or wounded since they have been moved from one tank to another. If any of the fish seem sluggish or has changes in the color, transfer the fish to a separate aquarium. This will give it time to restore to health and toughen itself.
Cycle your tank. Toxins like ammonia and nitrite tend to increase to excessive levels before the bacterial colony in your tank is sufficient to process the wastes. The beginning of the cycle has always been traditionally perceived to be the appearance of fish wastes. The cycling method required you to put in some tougher kinds of fish to facilitate cycling of the tank through their wastes.
For highly developed setups it is advisable to add all the fish at once. For the general community tank and beginners, it's best to add fish slowly about a few per week so that the bacterial colony has time to increase in harmony to the production of fish wastes. Go easy on your fish during the beginning of your tank. If anything unusual happens, consult someone who has expertise on the field.

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