You've set up your aquarium and the water has tested fine. It's time to run to the fish store and buy a bunch of fish, right? In reality, if you want to have a healthy aquarium, you need to take it one step at a time.

Before you go wild in the fish store, take a few moments to decide what species is best. You don't want to add an aggressive fish to a peaceful community tank. Keep your fish within the same size range because a larger one may end up taking a bite out of a smaller one. To find out what a mature fish of your chosen species is like, do a little research. A happy tank is stress-free, so make sure you pick fish that can live peacefully with each other.

You can avoid these sorts of problems by making sure the fish you're interested in are known to get along with the other kinds of fish you want. Make sure they are community fish that get long with others, if you want more than one species. Your fish selection should be based on the toleration of the same or similar water conditions. They should have the same taste in food and live aquarium plants.

Some fish, like damselfish, are territorial. They will prefer to be on their own, and will attempt to frighten off other fish that resemble it. Peace-loving fish like guppies don't disturb other fish by pursuing them or picking on them. Slower fish at times have problems when aggressive fish chase them or nip at their fins.

An aquarium with a species that tends to be aggressive wouldn't be a good environment for fish that are shy or slow as they would be bullied. Extremely vulnerable fish, like bubble-eye goldfish, may be picked on by almost any other fish, even if they are normally peaceful. Some fish that may grow aggressive as they mature should never be added to a tank with smaller or shy fish. As they mature they will start picking on the other fish, stressing them out and possibly causing them injury.

Also think about the durability of the fish. A hardy fish such as the blennyfish can resist multiple diseases and survive in various water conditions. A fish that is of average hardiness should do fine in a healthy aquarium. A fragile fish like a flagfin angel may fall victim to disease or stress if the water quality isn't just right.

Another key point is eating habits. An arrowana or an angler, which are carnivorous, will eat other fish. They are not something that you will want to add to a community aquarium. Herbivorous fish like angelfish need vegetables to eat, and may be harder to maintain in a healthy condition in a combination tank. An easy way to keep all of your fish on similar healthy diets, is to find fish that will be able to eat the same easily distributed foods, like pellets and or flakes.

A final item to consider is including some algea eaters in your aquarium. When it comes to keeping your aquarium clean, certain species of snails, shrimp or catfish can do a great job.

A lot must be considered prior to adding new aquarium fish. Be sure to discuss any questions you may have with the clerk at your local fish store. You can also get some good advice online. You'll end up with a healthy aquarium that you can enjoy.