I recently had an alkalinity swing creep up on my reef.  Normally I like to keep the tank around 8 dKH, and yesterday I noticed the duncans in my frag tank (part of the same system) were closed up. One bad habit I've developed over the years is to watch the corals for indication of problems instead of water tests each Saturday like I used to perform.  I need to get better about that.  I did a quick check with my Elos Alkalinity test kit and was shocked when it hit 21 dKH.  So I tested again, and it measured 19 dKH.  Safe to assume it was about 20, way too high.  I turned off the calcium reactor's output immediately, and let the solution within the body of the reactor recirculate so it didn't stagnate.  Today I did another test and the reef measures 18 dKH.  Since the number is quite high, I don't want to pull it down quickly and shock the SPS corals.  I'm thinking I'll bring it down to 15 dKH, then let the tank idle at that amount for about a week, then bring it down to 11 dKH and let it idle for a week.

The idea is to get that number back within line without losing corals in the process.  Bringing it all the way back to 8 dKH now would definitely kill some colonies.  Just wanted to share my thoughts with y'all, and I'll be sure to post an update in the future.&nbsp

Looking at the system, the corals really look normal.  The anemones are fluffy, the LPS are open. Even that Duncan colony from yesterday that looked closed up looked totally fine today.

So what caused this number to rise?  The only thing I can think of is that I cleaned out and refilled the calcium reactor with fresh media.  I didn't change the pH level within the reactor, which is set to 7.0.  I'm going to find the manual to change it to 7.5 now, so the solution coming out of the reactor will be less alkaline. (Hope that's the right term)