Now you need to add Stress Coat to the water. All tap water contains chlorine and possibly even chloramine. The Stress Coat will neutralize the chlorine. If you live in a large city and suspect that they are adding chloramine, you will be needing to use Ammo-Lock II with the Stress Coat. Chloramine is chlorine and ammonia combined.
Ammonia is the deadliest chemical for fish.
Adding Fish Now that your aquarium is up and running you can start to think about adding fish. Make sure that the temperature is about 78 degrees, the pH is 7.0, the aeration equipment is working, and the filters are working properly. One very important thing to remember at this time is not to add all your fish at once . You can about guarantee that they will die if you do. Gradually add a couple of fish each week until the bacteria in the undergravel filter has a chance to become established.