Just mixed up some IO, Ca not so good
 

Going to start trying to push up my Ca by supplementing along with the Ca reactor so figure a water change then get some good baselines.

Aerated and heated 20g ro/di for a couple of days, added salt Friday, brought up SG fr 1.023 to 1.025 yesterday and measured today (Sunday).

CA 325ppm (using Salifert and Elos)
Mg 1100ppm (ELOS)
Alk 11.2dKH (Salifert)
SG 1.025 refractometer.

Bought so many pails of salt the years so unsure when this pail was purchased but goes to show can't assume the Ca is that magic 425ppm.

Ouch!

Was this a new pail you opened, or one you've already been using?

IO salt has never been the "magic 425" with RO water. 350 tops. Looks like that water is fine to me. For a higher Ca content, try Kent. Also, there isn't anything maginc about 425. I've had great growth at 375 Ca. The magic is keeping it stable and in line with alk.

Been using for a bit. Probably why my reactor hasn't been keeping up.

Weird, I have been going thru just the same thing. Water changes seemed to be lowering my calcium. I tested the water in my mixing barrel ( 2 day old mix with IO and RO/DI) it tested at 300. This was using 2 different good up to date test kits.
Im swiching to Seachen Reefsalt.

does this meen you need to adjust the water for you're next water change to the same calcium level as you're tank water or does it balance out?

I always ran a reactor, so a 10% change didn't affect the levels that much. Using IO without a reactor or kalk, I'd probably use Kent A/B to adjust the makeup water. Or Kent salt, which is pretty much the same as IO but higher Ca.

I always add magnesium & calcium to my Instant Ocean mix. I follow the amounts tested by Ben, {chemmaster}, for his tanks and dont even bother measuring the mix anymore.

purple-up and kent liquid calicium are both the same thing right? aren't they both ionic calcium, because thats what i've been dosing for last couple months..

last batch of IO I mixed up left me with Ca at 325, ALK at 9.6 and Mg at 900.

Definately needs some extra buffer mixed in.