I have a 75 gal mixed reef (30 gal sump) that I do a 10 gal water change on every 2 weeks (ish). I've noticed that my alk consistently drops the day after the water changes. Between changes it stays 8.2-8.5, but after changes it drops to 7.7 or so. I test my fresh saltwater before my change and it is usually around 9.0, Fritz salt. This time it dropped from 8.7 (I was a little high for some reason) to 7.7.
If my saltwater is testing approximately where I want it, how do I prevent this? I don't see any new precipitate.
TIA
Cindy
If my saltwater is testing approximately where I want it, how do I prevent this? I don't see any new precipitate.
TIA
Cindy