The purpose of water change is to reduce the concentration of nitrates in the water, which are harmful substances to fish. It is assumed that if the index of harmful substances in this tank of water exceeds 7, fish will die. The current index in the tank is 3; if you feed the fish frequently this week, the index may rise to 5. If you do not change the water this week, the index will reach 7 by next week, which would be beyond the limit.
Impact of Water Change
Suppose the index is 5 in the first week, and I change one-fifth of the water; the index of harmful substances would then be reduced to 4. At this point, someone might question: this is not acceptable, I cannot tolerate an index of 4 harmful substances, I decide to replace all the water, resetting it to zero, wouldn’t that be better?
The Importance of Balance in the Nitrogen Cycle System
Risks of Complete Water Change: A complete water change can disrupt the balance of the nitrogen cycle system. Under such circumstances, nitrites cannot be decomposed in time, leading to the production of substances more harmful to fish. The accumulation rate of these harmful substances will accelerate. Within a week, or even before you change the water, the index of harmful substances could exceed the limit, causing fish to die.
On a certain morning, you may find the fish starting to swim belly-up, a moment of sadness in your heart, and all you can do is feed it to your beloved turtle.
Original article by KPTer, if reproduced, please cite the source: https://www.kaipet.com/en/purpose-function-aquarium-water-change-importance-maintaining-water-quality-balance
