The Nitrogen Cycle

• Fish release ammonia into the aquarium water through their gills, waste, and uneaten food. This ammonia is very toxic to the fish and is a leading cause of death. Fortunately, there are good bacteria that colonize the tank and convert the ammonia into nitrite, which is also toxic to the fish. Other bacteria convert the nitrite to nitrate, which is relatively safe for the fish.
• Every time you add a fish to your aquarium it releases more ammonia into the aquarium than your current population of bacteria can handle. It takes time for more bacteria develop to take care of the increased ammonia levels. If ammonia levels rise too quickly, the bacteria may not be able to keep up and your fish may quickly die of ammonia poisoning or be more vulnerable to other diseases, so only add a few fish to your aquarium at a time and be careful not to overfeed them.
• When you are starting a new aquarium, add fish very slowly- just one or two at a time. Be especially careful during the first six weeks. Test your water before you add a new fish-- new fish are more likely to die in toxic waters than fish that are already established in the aquarium.
• You can get bacteria starters that will seed the aquarium with bacteria and help the biological filtration process get started, but this doesn't replace the need to be patient and add fish slowly. It still takes time.

Adding New Fish

• When you add your fish, float the bag in your tank for about 15 minutes so that your fish is not shocked by a drastic temperature change.
• Watch to be sure that your other fish don't pick on the newcomer. Fish are curious and may come close to investigate, but watch out for biting or other signs of agression.
• Being moved to a new tank puts the fish under a lot of stress. Adding a protective slime can help beef up the fish's disease resistance.
• Sometimes adding food to the tank when you release a new fish can draw attention away from the newcomer and give him a few minutes to settle in.

Maintenance

• Regular maintenance is essential to your fish's health. I recommend cleaning your tank once every two weeks. Cleaning your tank shouldn't take very long at all. Here's what to do:
• Decide what day you want to clean your tank. It is easier to remember if you have a regular schedule.
• The day before you clean, wipe down the inside walls of the aquarium with an algae scrubber that is appropriate for your aquarium(some will scratch acrilic surfaces). Even if you don't see algae yet, it is forming and regular cleaning will help keep it from growing. Doing this the day before permits debris to settle to the bottom of the tank to be cleaned out when you vacuum. You can do it all on the same day if you prefer.
• Turn off the filter and heater and allow the heater time to cool off (about 15 minutes) before you remove any water. Use a gravel vacuum to remove the debris from the top 1/2" of the gravel. The gravel vacuum allows you to clean the gravel without disturbing the good bacteria that live in it. Remove about 25% of the water when you vacuum (removing too much at once can be harmful to the fish). This is a good time to clean or rearrange plants and decorations. Fill the tank with clean, dechlorinated tap water. The water you use should be about the same temperature as the water in your tank. Restart your filtration and allow time for the heater to adjust to any temperature changes before you plug it back in.
• If you have a power filter, the cartridges should be replaced every 3-5 weeks.
• Charcoal should to be replaced every 4-6 weeks.
• Airstones need to be cleaned or replaced every 4-6 weeks to keep the pump functioning properly.
• Check the temperature in your aquarium at least once a week. Slowly make any needed adjustments.

Next:  Fish Health, Disease, Treatment, and a run down of common diseases--->