Distilled water is not good for fish - Fish need some minerals in the tank. Plus the lack of HCO3 (KH
) in the water means you will have unstable pH & tank crashes.
Adding chemicals to balance out the water is generally not the solution, unless you know what your nasties are & you are adding stuff to precipitate (ie remove) the unwanted stuff, and not just masking their presence.
Have a complete test of your well water (before & after treatment). You should have this done by a professional lab (rather than hobbyist home kits as these are not really accurate or complete.) You want these numbers so you will know if you want to use your water at home, not just for your fish.
If the water test is reasonable <pay attention to nitrates & nitrites & phosphates, low levels are OK for human consumption, but not good for fish .... ditto for HCO3,CO3,Ca
- levels may not be OK for fish even though it says OK for people.> , you can use that for your tank (and drinking too, perhaps after filtering).
If water is bad - I would go reverse osmosis. You can get a unit fairly cheaply, and the resulting water has all nasties removed (almost as good as distilled, but much cheaper). This is the route my inlaws had to go with their well water (high NO3
& others). You can safely drink R/O water, although for fish tank, you would need to add some buffering capacity to prevent pH swings. You can buy salt mixes (for fresh water!!! not SW
) for adding to R/O or distilled water, or go cheap & add crushed coral to your tank.