Sadly, this has been a problem I've been battling for awhile. Water changes have not solved it. My Ca
is 600, do not have a mag test. pH would be a light 7.8.
I do 10% water changes weekly on my 55 mixed reef w/ 20 long sump/refugium. There is a dual reactor running purigen, anti-phosphate+nitrate along with chemipure along side my oversided reef octopus skimmer rated at 150 gallons. The tank itself is well stocked with corals, but not near enough to be absorbing this amount of alk
without the calcium. This is known to be true as this is a constant issue in this system and have battled alk
before, changing salt mixes to have a higher calc/alk
than normal IO or reef crystals to Kent.