High nitrate accumulation, sometimes referred to as old tank syndrome, can be a common problem for long time aquarium hobbyists. It usually occurs when regular maintenance and water change routines are ignored.
This nitrate reduction method is an instant nitrate reduction water change method. You can reduce nitrates quickly to zero with no ill or harmful effects to established aquarium residents. In fact, the behavior of the tank inhabitants can improve greatly afterward. You may notice the fish will become more active, start eating better, and may display brighter colors within a few days.
One important consideration before you start a massive (or any, for that matter) water change is to remember that you will also be changing the pH in your tank (probably upwards). Before beginning this water change, it is wise to slowly adjust your tank water pH to where it will be when you are finished. You can adjust the pH upward with common baking soda, or downward with one of the many products on the market to reduce the pH of aquarium water. This will prevent your tank critter from going through "pH shock," which can be fatal to more sensitive tank critters.
This method was proven when an experiment was performed to test it. The test tank's nitrates were allowed to rise to a dangerously high level, literally off the scale, to observe the transitions the tank would go through. The experiment was successful. It allowed the testers to observe the formation of different algae.
The established aquarium residents survived, too; a 15" snowflake eel, various types of hermit crabs and snails, a few crabs, two colonies of zoanthids, some non-living corals, and some live rock. The testers even added a newly mated pair of coral banded shrimp the day after completion of the water change procedure with no problems at all.