Your
ca levels shouldn’t change that drastically in 3 days with 100
gal total water volume. Dose on the higher end before leaving ie: 450
ppm ca and I would be shocked if it dropped past 380
ppm in just 3 days. You wouldn’t want to come back after 3+ days and have your
ca 500+ with your
ph at <7 and dead fish/inverts.
You could try a trial run for a couple of weeks monitoring daily to get the dose right but for long term I wouldn’t risk it personally. To many variables to go wrong.
As said by many people “good things happen slowly with
sw and bad things happen quickly” If you don’t have the “time” for hard corals then maybe you shouldn’t get any.