ALK Issue - HELP!

[ThePriceSeliger]

I'm having serious discrepancies in my ALK. In my mixing container, it measures 9.0-9.2dKH. In my DT it measures 5.6-5.8dKH. I have an automatic water change doing .5gallons a day three times a day. I'm using Red Sea Coral Pro salt.

My refractrometer measures my salinity at 1.024. My LFS measures my salt at 1.029

DT:
ph - 8.2
Cal - 400
Mag - 1270
dHK - 5.8-5.8

These results were tested by the LFS and myself.

The tank is new, it's been running for over a month now. I have three SPS frags, a handful of zoas and one LPS, two clowns and a blenny. Everything looks healthy accept for an acro I picked up a few days ago.

What could be causing this?!!?!?

 

[Randy Holmes-Farley Verified Community Expert]

It is normal for alkalinity to decline in reef tanks for at least two important reasons (coral skeleton formation, and nitrification of ammonia), and so one generally has to supplement it.

This has more:

The “How To†Guide to Reef Aquarium Chemistry for Beginners Part 2: What Chemicals Must be Supplemented by Randy Holmes-Farley - Reefkeeping.com

 

[ThePriceSeliger]

And that I completely understand, but that seems like a pretty huge drop for the small amount of activity in the tank. That is what has me stumped.

 

[Randy Holmes-Farley Verified Community Expert]

It would be a big drop in a day or two, but in 30 days, that's only like 0.1 dKH per day.

Once it revs up, it might use 10-50 times as much per day.

 

[ThePriceSeliger]

Thank you Randy. Also, I know you're using an autmated water change system. Do you notice any different needs in required dosing due to the continual replacement of FSW?

 

[Randy Holmes-Farley Verified Community Expert]

There will be an effect, but do not see it because I never measure alkalinity or calcium.

I just know from years of running the system that replacing all evaporated water with limewater works. I used to measure them, but not in the last few years.