One of the most detrimental aspects to good fish health is constant swings in water parameters. Once your tank is established, maintaining stable water conditions should be one of your first priorities. I consistently see cichlid keepers, typically newer ones in the hobby, struggling to understand why sudden changes occur in their water parameters. How does this happen and how can it be prevented?
Those are actually two separate questions. How it happens is more difficult to answer than how to prevent it. Why? Because there are any number of reasons wild swings can occur. From overfeeding to introducing too many fish and overloading the bioload to undetected dead fish and pH crashes from big water changes. Thus there are myriad reasons that stable water becomes unstable and starts to “go south” as we say in my section of the country.
So how to do you prevent it? The single best thing to do is keep a consistent maintenance and water change routine. It’s that simple. Once your tank is cycled (assuming it was cycled), do your maintenance on a regular schedule and perform the same tasks. Change your water on roughly the same schedule and do the same percentage of change each time. And keep an eye on your tanks. If you’re familiar with your fishes’ behavior, you should notice issues before they become problems. That shouldn’t be hard.
I currently maintain nine tanks from 75g to 20g. I change the same percentage of water volume in each tank with every weekly water change. I also do the water changes on the same schedule (e.g., day of the week). When you add water to your tank, use the same amount of water conditioner if you’re on municipal water (i.e., treated water). Doing all of the above, I have NEVER experienced a parameter crash or spike. And I’ve been doing this for over 20 years.
Sure, there will be times when you make substrate changes, add ornaments, ceramic or plastic caves, live plants, artificial plants, or rearrange everything, etc. None of those activities should cause problems. Let me repeat that. NONE of those should cause major water parameter changes, certainly not enough to start losing fish.
The name of the game is “stability,” and stability is created by being consistent. So when your tank crashes, ask yourself what you did the days prior that you don’t normally do. The bottom line is develop consistent habits and maintain them.