Originally Posted by ERDoclovesfish
Should we avoid salts that contain borate which would further complicate matters? So Normal calcium w low DK add buffer, Low Calcium w normal buffer add calcium and buffer, low calcium and low DK add calcium and buffer?
There are a lot of different opinions on this, but is you read carefully what Randy Holmes Farley is recommending, you just missed it....
Normal Calcium w low DKH... adding a buffer probably won't work. In this case the simplest action is to do a partial water change. If you are doing regular water changes, you probably won't get this situation because the presence of borate salts and magnesium should be adequate. Many hobbyists test for magnesium, although R.H.F. says it is probably not necessary.
Low Calcium w normal DKH... add calcium only. If you add the buffer also, you will continue to have readings outside the recommended zone. In fact, this is where you should be adding something like Kent Marines Liquid Calcium supplement, or the Calcium-only part of the B-ionic product. No buffer.
Low Calcium and low DKH... add calcium and add a buffer. The B-ionic product is perfect in this situation.
Here are the 2 links that really break this down: Reef Aquarist: The pH and Alkalinity Can Vary For Different Reasons RandyHolmesFarley Alkalinity
Randy recommends not using a salt high in borate because it makes the equation more complicated. Reef Crystals is an example of a salt that has 100x the natural levels of borate.