Help with ALK not lowering

[dunc101]

I have a strange problem that I personally haven't seen anyone post about or encountered myself before. My alk is not falling even though I'm not dosing any ALK or CA , my water in my water change water is 6.7 and have around 50 pieces of SPS that should be consuming alkalinity and calcium (1-4 inch frags for the most part). They are definitely growing and encrusting the plugs well.

Background.
Tank Size: 80 gallons with 40 gallon breeder sump.
ALK: 8.6 - Cross checked with 2 Salifert Alk Test kits to verify.
CA: 470 (high as well and this isn't lowering either)
PH: 8.0-8.25 or so according to my Apex
Water changes: 1.1 gallons a day (Auto water change via Apex DOS.). The alkalinity in this water is 6.7 dkh (HW Marinemix salt)... Cross checked with 2 salifter Alk tests.
Age of Tank: 10 months

I'm running a Zeovit system (using the main 3 daily) and need my ALK in the lower 7 dkh range. I'm starting to have a few frags slowly STN and need to get the ALK back down in the "safe" range.
Other than doing a few massive water changes I'm not sure what to do. Even then, if my alkalinity creeps back up I'd be in the same place so I'm hoping someone could give some pointers?

The only thing I can think of is the rock I am using is leaching alkalinity and/or excess calcium? I used the same rock in my old 90 gallon before I moved which I dosed around 120ml of ALK and CA a day. Could these rocks have ALK and CA residue left over that is "leaching" out?

As far as sand goes, I have 30 lbs of Tropic Eden Reefflakes. Could this be part of it?

Thanks for any help!

 

[Randy Holmes-Farley]

You can lower it if you want, but I do not think the problems with high alk and low nutrients (such as burnt tips) are likely to occur when no calcification is yet taking place. The hypothesized mechanism is that calcification takes place too fast and tissue growth cannot keep up.

SO while there are ways to lower alk, I'd just watch and wait if it were me. :)

No, there's no alkalinity leaching from the rocks, unless they are artificial rocks. Not sand either.