Originally Posted by bouncer36
Reverse osmosis de-ionised water. Basically water filtered until it contains no other elements. 100% water. You then have to remineralise it, so you can get the exact water parameters you require.
Regards your question about pH. Fish live in a wide variety of pH, it doesnt have to be neutral. Unless you are keeping fish that require a very specific pH (like discus or cichlids) fish will acclimate to the pH. I have pH around 7.2 to 7.5 so your pH of 7.6 should be fine. Its better to keep the pH stable than it is to keep raising and lowering it looking for a specific number.
Your local fish store will likely be using the same water you are (although some might use rodi
) so the fish they sell will probably already be acclimated to whatever pH that is.