It seems like early Spring and late Fall there is a naturally occurring change to water parameters and fish seem to come down with more disease that other time of the year. Knowing what to watch for can help reduce stress on your fish and potentially avoid disease.
How Much Water to Change
This is a difficult question to answer directly as what works for one may not work for another. But, here’s how you can judge it. Monitor your water parameters and compare it to your source water.
If you are lucky enough to have no nitrogen waste in the source water, then you can…..
- Monitor ammonia and nitrite to ensure the cycle is stable
- If you are not housing nitrogen sensitive species you can hold off on water changes until the Nitrates test above 40 ppm (20 ppm with sensitive species)
- Is your tank planted? Then monitor KH and GH as plants can consume these water components and cause the pH to destabilize.
Increased Chlorine or Chloramine Smell?
In the Spring many water treatment plants often flush their systems. And the sudden increase in chlorine or chloramine may require extra dechlorinator than is normal. There are test kits to monitor chlorine, but the best test is your nose. If using a water conditioner such as Seachem Prime, it can be safely dosed 5 times normal strength when needed. Better safe to use extra conditioner than to have dead fish.
Heavy Rainfall or Recent Snow Runoff?
This can change the general water chemistry. A quick water test can help determine if the pH and other parameters have changed or remain stable. For me, I have two different water sources. One source I get about 9 months out of the year. It comes from a local spring with very soft, low pH water and my other source is moderately hard water that is high in minerals, high pH, high Phosphate, high Iron, and even comes with a bonus of radioactive Radon due to the surrounding volcanoes. If I’m not careful when the source water changes a large water change can kill my fish. Unfortunately, this has happened to me more than once. I lost thousands in rare, irreplaceable fish.
If on municipal/city water also monitor the annual water reports. Most will post the reports online, but not all do. And monitor for changes. Starting in 2026, my water company has decided to start adding Caustic Soda to jack up the pH. So my tanks went from 6.4 up to 7.8 overnight. And what is most irritating is they are claiming it is healthy for us to drink; yet they are required to remove the Caustic Soda from waste water before returning it to the wild.
If on well water, you don’t have to deal with chlorine, chloramine or any other additives used in the city; however, you do deal with possible pesticides, chemical fertilizers and other contaminants. So, while you may be able to get away with no water conditioners you do need to be aware and periodically test the well water. My parents had issues with their well. State had them pour bleach and all kinds of other chemicals into the well to make the water safe. And they still can’t drink it!
Have you recently moved?
Doesn’t matter if in the same town or across the country. Every water source can have some difference; different pipes can affect water chemistry as well. Again, knowing what you are dealing with and how close it matches your tank parameters is all that is needed to make educated adjustments to keep your fish safe at all times.
Periodically test your source water to determine what is normal. Does it contain high levels of minerals? Does it hold heavy metals? You can obtain the basic details of your water chemistry from your municipal water company or by paying for a water analysis if on a well. Or, can use a test kit, such as the API Master Kit plus the GH and KH tests for a good overall general analysis of your source water.
Compare these results with your tank parameters. If things are being well maintained then both the source and the tank water should have similar parameters. And stable parameters in the proper range is the key to long term health of your fish.
For example, are there any measurable ammonia or nitrites? If so, your tank may not be cycled, it may be under-filtered or the cycle may be wobbling and unstable. Simple enough to fix if you know what is leading to measurable ammonia and/or nitrite. Both should always be undetectable.
Nitrates over 40ppm? Housing Species Sensitive to Waste? Dealing with Disease?
Then, need to step up maintenance to better manage waste buildup and keep the environment clean. There are far too many who think they never need to do a water change. And then wonder why every new purchase dies in a day or two. And simply blame the store or breeder for the losses. Fish are very adaptable when exposed to something slowly over time, but drop in new fish and they can’t survive, what is to them, a toxic environment. Fish rely on the minerals in water to meet their physical needs for growth. If you are one of those to think along this line, then ask yourself why you keep your own house clean, but not do the same for your fish.
By providing a healthy environment along with a variety of high quality foods you will be able to enjoy your fish for a long time, free of disease.