Adding a significant amount of pH up or down can cause root damage, burning the fine root hairs and setting the plants back while they recover. I use a 3 gallon bucket with a piece of 1/8" vacuum hose attached through the side near the bottom. I put a gallon or so of RO into the bucket, add my pH adjuster, mix, and let it lowly drip into my system. It generally takes about 30 minutes for the whole gallon to drip into the system. Since I'm running RDWC, the constant circulation allows the pH adjusting solution to be gently circulated and doesn't subject the plants to being shocked by a sudden pH change.
