Different water will have a different impact on the fish in your fish tank. I recommend using the highest quality water you have available.
For many people this means well water, which raises an interesting question, can well water be used in a fish tank?
Yes, you can use well water in a fish tank assuming that it does not have any contaminants and no salt in it. Basically, it just depends on the quality of your well water. If you have poor quality well water, then you can always just treat it to remove any contaminants.
The Problem With Well Water in a Fish Tank
As mentioned previously, you can use well water in a fish tank.
I don’t recommend it, however, as it requires a decent amount of treatment in order to guarantee the safety of your fish.
For instance, well water contains significantly more minerals and total dissolved solids (TDS) than normal tap water.
This makes sense because well water comes from the ground and does not receive any treatment.
Now, minerals in water is oftentimes good for humans.
It’s not good for fish, though. Fish are fairly sensitive to minerals and can easily die if you put them in water that has a human healthy amount of minerals in it.
Other problems with well water include the pH being vastly different depending on the particular well, the amount of ammonia or nitrates in the water (common in areas with a lot of farming), and other contaminants that seep into the water table from runoff.
How To Use Well Water in a Fish Tank
If you really want to use well water in a fish tank, then you will first have to test it for various contaminants. You will also have to test the pH level of the water.
If you find any TDS or other contaminants, then you will have to use a reverse osmosis filtration system to remove them from the water.
That’s a lot of work to use water in a fish tank.
I find it easier to just use tap water and let it sit for a few days to remove the chlorine. I know that’s not an option for everyone (ie. large fish tank in a rural area), but it’s by far the best option if you have it.
Well Water in a Saltwater Fish Tank
Saltwater fish are even more sensitive to contaminants in water than freshwater fish.
I strongly recommend not using well water in a saltwater fish tank. If you have to use it, then you will have to take into consideration all the different contaminants, TDS, and minerals found in the water. Well water generally has more CO2 in it than tap water, so take that into consideration as well.
You don’t want any of that in your fish tank’s water. You will also have to check the water parameters before every water change as normally ok well water can become contaminated due to runoff or other issues underground.
To summarize, you can use well water in a fish tank without issue, but it requires a decent amount of preparation and testing before use to ensure maximum safety for your fish.
Due to all the prep work, I do not recommend it unless necessary. For instance, if you have a 10 gallon tank, then you are much better off just purchasing reverse osmosis water from a grocery store than going through the entire process to ensure you have fish friendly well water.