With basic knowledge of aquarium maintenance and tropical fish husbandry, anyone can create and propagate a self contained aquatic environment that can provide hours of enjoyment and relaxation. Medical research has shown that aquariums can be effective stress management tools; that is, reduced anxiety levels and lowered blood pressure can result from spending just a few minutes every day observing the steady, flowing movement of aquatic life.
There are three types of environments that tropical fish hobbyists can choose from: Fresh Water, Brackish Water, & Salt Water.
Given the large variety of tropical fish available in the pet trade, I will not attempt to offer advice on what fish you should keep with what other fish. Always tell your pet store what fish you have before purchasing a new variety. Hopefully, they will be well trained to advise you. As a general rule, and I mean very general, You can have one inch of fish per gallon. If you have a 10 gallon tank, you can have 101" fish or 5- 2" fish, etc.
When you bring home your new fish, keep them in the bag and place the entire bag in the aquarium and float it for about 15 minutes so the temperatures are about the same to avoid shock. Open the bag, and let slowly let the water from the bag and the tank exchange. They should swim out of the bag into the tank. Do not leave the tank unattended during this process, as you may need to coax them out of the bag if you notice any gasping. | 
