It's technically calcium hydroxide so most LFS should have it.

I bought 50lbs of it from the sponsor Fiji Reef Rock a few years ago so I'll never have to worry about purchasing it again.

Most likely do, but it's expensive as a retail aquarium product. I used to buy it from a member here for $5 per grocery bag :)

I have a 1gallon almost full of BRS Calcium hydroxide that I'm not using
$10 or a nice frag if your interested. :smile:

I had a beautiful 90g reef that I only ever supplemented with kalkwasser. On this tank it was plumbed through the ATO.

I'm not presently using it, but from my experience I wouldn't connect it to the ATO again. Rather I would use a dosing pump to control the rate of adding it and a seperate ATO on its own. Top up is somewhat unpredictable and prone to fluctuations. In my case, I had a random ATO pump failure while I was away on vacation. The tank sitter discovered it and fixed the pump. Of course the water level had dropped and he added a couple of days of evap back into the tank all within a 10 minute period. The ph shot up to something like 12!

Keep some vinegar on hand in case something like this ever does happen. We added vinegar slowy over the next hour to bring the ph down. There were no losses, just lessons learned.

Brad