In my reef tanks I always top off the tank with RO/DI water which has 0 tds. I do this because only the H2O evaporates not the salt or other minerals, etc... in the water.
My tank water was at 8.4KH. When I toped of my 55 with more 8.4KH tap, the tank KH increased to 10KH. I'm wondering if I should top off with RO/DI water to keep the KH from increasing. (I would still use tap for water changes)
Does this make sense? Does anyone use RO or distilled water in their tanks?