Wise girl. Adding too much PH down WILL HURT your
fish! PH down is acid and too much acid in the
water will burn the fins right off your poor
betta! (yikes!). A PH of 8.4 is pretty darn hard,
granted, but bettas are incredibly forgiving when
it comes to PH. In California, we have a high PH
of about 7.8 to 8.2 and our bettas do just fine.
If you only have one or a few bettas, you could
consider acquiring an R/O system (Reverse
Osmosis). What it does is it takes tap water and
purifies it by forcing the water through a diaphragm
(no, not THAT kind of diaphragm LOL) and other
filters that will retain most of the minerals in
suspension. Resulting in purified water that is
more acidic and with a very low PH (6.0 or
something) and a hardness usually around 30 to 60
ppm. Such water is not good for bettas but it is
great when mixed with your hard tap water because
it will cut down the PH and hardness in half.
Meaning your PH will be around 7.0 and your
hardness around 200 (as opposed to 400 or so).
This is the best way to correct a very extreme
water hardness. Cost of R/O systems vary, for a
few fish you don't need a very powerful one since
you will not need a large volume of water. I think
maybe around $70 to $100 you should be able to get
one. Maybe less. Don't quote me on this quote LOL.
If you are unable to spend that kind of money (but
that would be well spent money), then I say just
add PH down, no more than 2 drops per gallon and
leave it at that. Make sure when you get bettas
from out of state to acclimate them VERY SLOW (for
example, take 2 to 3 days to switch them to your
water). Good luck to you and your bettas !