First I would suggest using a second DKH test but you mentioned using API and Salifert. You should test your new water for DKH before adding to display. You might have picked up a batch of salt with Higher DKH then normal. You say nothing is being doesd into the tank. The only way for the DKH to rise is from water changes. It must be the bag of salt you are using. Like the others posted low MAG will make CAL and ALK unstable.
I may be wrong as I have never used that ESV product, but if you are adding calcium carbonate, that is your problem. It sounds like you should be adding calcium chloride to boost your Ca:Mg ratio as to not increase alkalinity.Update:
Mg- 1300 still
Ca- 340 still
Alk- 15-16 still
Still only dosing B-Ionic Ca supplement and Oceans Blend Mg
I may be wrong as I have never used that ESV product, but if you are adding calcium carbonate, that is your problem. It sounds like you should be adding calcium chloride to boost your Ca:Mg ratio as to not increase alkalinity.
if that alk would drop you would be dancing in heaven !
ok.... so now im completly lost.
The regular... RO / DI water is coming out with a alk of 18...
I get the water from the LFS, they use it on there 100+ tanks and dont seem to have 1 issue whatsoever.
now accepting donations for a RO / DI unit so i can put it in my house. HA