jeffaquarius
Aquarium Advice Addict
Tying things back to my original comment towards the OP in an attempt to get this thread back on track: The parameters in freshly mixed water are often a fair amount different than your tank values due to co2, slightly depleted mineral levels, and whatnot. It doesn't make hardly any difference in a smaller change of 50% or less but in a larger water change (such as the suggested 95%) those differences can be drastic.
Well, you are assuming that all the 90% new water is poured to the tank instantly and not left overnight before the pwc. Of course you need to use a small hose with pump to slowly fill up the tank. Anyway, the OP has already decided to keep up the 25% pwc so I would leave it that way.