If there are no existing fish, then there are no good bacteria. The basic principle of the nitrogen cycle is this. Fish eat food and generate waste. That waste along with excess food and plant debris become ammonia in the aquarium. Ammonia is toxic to fish and needs to be broken down. That's why the nitrifying bacteria is important. Coldwater Aquarium Set-up and Care As the hobby of having an aquarium becomes more and more popular, it should be noted that the easiest aquarium to care for and set up is a coldwater tank. As the name suggests, coldwater tanks require no heating set up. This cuts costs when setting up your first tank. This type of solution is available at most pet stores. Salinity of the tank should be between 1.023 and 1.004. Ideal temperature for a marine aquarium is between 75 and 79 degrees Fahrenheit. It is also important to test the P.H. of the tank. Ideal P.H. is somewhere between 8.3 and 8.4. Test kits can be purchased online or at your local pet store. The water from the tank may be disposed in a sink or toilet. This can be a messy task, so be sure to clean up all spills to prevent any possible accidents. It is not necessary to remove all the water from the tank. Most freshwater aquarium owners remove approximately 3/4 of the water. The remaining original water will help acclimate the new water you will add later. Check to see that all lights and filters on the aquarium are plugged in and functioning correctly. Feed the fish daily. Only feed what can be consumed in the first two to five minutes. Any excess food will become debris in the tank and lead to illness or attribute to excess nitrite levels. You should check the water ph and temp weekly. An aquarium is less of a commitment than larger pets, and can still be a welcome addition to the family home. Aquariums are great learning tools for small children. Kids get excited if they are involved in process. They can learn responsibility by having to help with the chores associated with aquarium care.