Aquarium pH & Alkalinity Regulation
Aquarium pH regulation is one of your first concerns - you must match the pH from fish store closely (ask for a pH reading) so your fish survives the transition to your own tank. After that it's up to you to maintain proper, stable pH. If you use pH regulators, be careful: big changes over short periods are fatal to most organisms. Most fishes can adapt to a wider range of pH than ideal as long as they are allowed to adapt slowly.
When greatly lowered pH is desired, consider using a reverse osmosis filter. When greatly raised pH is needed, crushed coral substrate in your tank or filter has lasting effects. Also see our freshwater buffers, saltwater buffers or reef buffers for lasting pH stability.