Originally Posted by jellopuddinpop
Iím not trying to hijack this thread (sorry OP!), but assuming remineralized RO water and buffering substrate, how do you control the ph of water for a water change? Letís assume the ph of the tank water is buffered down to 6.0 by the substrate, almond leaves, alder cones, etcÖ and the RO water is sitting stable at 7.0, can you just change 25% and assume all will be OK? Wonít that result is a sharp jump in the ph of the tank? I understand the tank will re-buffer to 6.0ish, but what about in the meantime?
I only ask because I plan on setting up some CRS tanks soon, and I've yet to understand this.
How much of an increase depends on how quickly you change the water (I'd drip change for smaller tanks). Your substrate will begin buffering the water as soon as you start changing it, so the slower you change, the more time you give it to keep up.
I don't like buffering substrates because they are expensive and require a tank teardown every year and a half to two years, but as Zoidburg mentioned, it will make your life a lot easier if you are just starting out. For smaller tanks, the cost might be worth it.
Personally, I don't care about pH that much, but if I did, I would pretreat my water with peat moss and then remove any tannins with a resin like Purigen. That's exactly what Diana was doing for her tanks, and peat moss actually lowers TDS unlike driftwood, IAL, or cones.