I have a pH of 8.2 as well.
The pH measures the Acidity and Basic-ness of your water. In Chemistry the pH scale is 0 for the most acidic like Hydrochloric acid to 7 Which is neutral to 14 which is the most basic such as Bleach.
The ideal for an Aquarium, depending on what fish species you want to keep is between 6.5-7.8.
Have you checked the pH of your tape water? If you have gravel in your tank, depending on the type that can raise the pH.
The pH affects how comfortable the fish is in it`s environment. A pH that is to far outside of a fish`s preferred range will cause the fish to be unhappy, sometimes, if the fish is sensitive or the pH range is to great the fish will actually die with no apparent cause other than the habitat was simply not suitable for it.
Indeed a pH of 8.2 will cause fish to not breed, that`s the only good thing about pH of 8.2 with Live bearers, they don`t breed more quickly than rabbits.
Once they get acclimated to the water most fish go on and live happy lives, however they may not breed. (I haven`t had fry in months, which is nice, but also makes me aware that my fish may not be as happy as they could be.)
You don`t neeed to lower the pH, if you don`t want fry up the wazoo than leave the pH where it is and your Platy`s wont breed. If you do want fry than I recommend getting Reverse Osmosis water. Or even Rain water if you want to be totally clean. Rain water and RO water is called soft water, and it will dilute the pH in your tank because it`s pH (Should in theory, unless there is contamination) hover around the magic, neutral number 7.
You can order an Aquarium Specific RO unit for your tank, or you can find a local Water shop and buy large containers of RO water, (Or go to walmart, big clear plastic containers of RO are available for purchase and you can dilute your own tap water that way.)
I do not recommend buying any commercial chemicals that claim to lower the pH, they will for a few hours to a few days max and then the pH will shoot right back up, that much shift in pH over such a short time will be harmful to your fish.
The safest way to lower pH is to slowly start introducing a pH neutral water to your water changes and add some bog wood if you want (Though beware of Tannin (I believe it's called
) in newly purchased bog wood as it will turn the tank water brown - it isn't harmful at all, it just makes the tank look dirty)
(of course I would get a much bigger tank if one of them did get pregnant)
