1. Always unplug all electrical accessories before you attempt to remove water from the tank.

2. Do not remove all of the water at one time; this will destroy the ecosystem that you have worked so hard to build up.

3. Using a plastic siphon device such as the Tetra Hydro-Clean®, begin a pumping action to drain about 20 percent of the existing tank water into the classroom sink or a plastic bucket.  Note: A five-gallon bucket is the perfect size for water changes.

4. Empty the bucket, rinse it out and refill with replacement water, which should be the same temperature as the aquarium.  Use your finger to test back and forth from the tank to the bucket, adding warm and cool water as necessary, until temperature seems equal.

5. To dechlorinate the replacement water, add 1½ teaspoons of Tetra AquaSafe®.

6. Gently pour the replacement water into the tank.

7. Plug in electrical accessories.

A Special Note:
How to Minimize the Risk of Pollution in the Classroom Aquarium

The three chief causes of ammonia and nitrite poisoning are:

1. Overcrowding of the tank - due either to the presence of an excessive number of fish OR of fish too large to be comfortably housed in the tank (the rule of thumb is one inch of adult fish for every gallon of water in the tank);

2. Malfunctioning of the filtration system;

3. Overfeeding.