RAPID Alk drops - where's it going?

Discussion in 'Water Chemistry' started by DeeBee, Oct 19, 2014.

to remove this notice and enjoy 3reef content with less ads. 3reef membership is free.

  1. DeeBee

    DeeBee Astrea Snail

    Joined:
    Sep 4, 2012
    Messages:
    54
    Location:
    Charlotte, NC
    For the past two months I have been having a constant battle keeping my Alk much above 7dkh for any length of time. The problem isn't so much getting the water to the 9 - 10dKH levels I want so badly but rather it is keeping it anywhere near those numbers.

    As an example this evening I manually dosed enough BRS soda ash to get my tank to 10dKH (tested with Red Sea and Salifert kits). This was at 5:00pm. I retested at 9:00pm and my water was now showing 8.1dKh! So within 4 hours my Alkalinity dropped by nearly 2 points!!!

    Of course magnesium would be the first culprit although I'm not sure I could even get my tank to 10dKH if my magnesium was low enough that it would precipitate that much out. However my magnesium is always above 1300ppm. When I tested it this evening it was around 1350ppm.

    My calcium levels stay consistently within the 420ppm range without a problem. No worries there.

    Tanks stats:

    57 Gallon with 20g sump (estimated 55-60g total volume) Light to moderately stocked. No clams, very little coralline algae, mostly LPS - only a couple small SPS
    Calcium: 420
    Mg: 1350
    Alk: 7.0 - 7.2 (on average)
    PH: 8.3 - 8.4

    I am dosing around 100ml of BRS two-part each night for a relatively small tank that is lightly stocked and still end up around 7dKH the next morning. That seems like a huge amount.

    I'm really stumped as to what I am doing wrong or what is absorbing the Alk. I used to be able to maintain all the levels without a problem so not sure what changed. And it isn't caked onto my heaters or pumps. What could cause it to drop so rapidly?

    Appreciate any input.
     
  2. Click Here!

  3. Av8Bluewater

    Av8Bluewater Giant Squid

    Joined:
    Aug 27, 2008
    Messages:
    3,401
    Location:
    Dallas
    Yeah that is weird. Maybe the mag test is off. Try bumping the mag up to 1450 and see what happens.
     
  4. Billme

    Billme Eyelash Blennie

    Joined:
    Sep 9, 2013
    Messages:
    1,260
    Location:
    Bakersfield, Ca
    What do you have for sand and rock?
     
  5. floydie83

    floydie83 Flamingo Tongue

    Joined:
    Jan 25, 2010
    Messages:
    106
    Location:
    Lafayette, LA
    My first thought was test mag again as well.
     
  6. Pdxile

    Pdxile Coral Banded Shrimp

    Joined:
    Nov 1, 2013
    Messages:
    363
    Location:
    Oregon Coast
    My first thought is a lot of bacterial action in your tank depleting the alk rapidly. But not that rapidly!
     
  7. ingtar_shinowa

    ingtar_shinowa Giant Squid

    Joined:
    Jun 13, 2009
    Messages:
    7,072
    Location:
    Billings Montana
    Is it precipitating out? is there a white film on your sump equipment or a "snow" forming after dosing?
     
  8. Click Here!

  9. ReefBruh

    ReefBruh Giant Squid

    Joined:
    Jul 11, 2010
    Messages:
    4,813
    Location:
    Clearwater, FL
    You might have to drop your mag to around 1280. Your levels are almost close to NSW. We all know that cal and mag work inversely with Alk so maybe lowering the others will allow it to rise. Just a thought.
     
  10. DSC reef

    DSC reef Giant Squid

    Joined:
    Dec 16, 2012
    Messages:
    3,814
    Location:
    Cocoa, Florida
    That seems like an awful big drop and since it just started to become an issue I'm wondering if your alk results are accurate?
     
  11. Vinnyboombatz

    Vinnyboombatz Giant Squid

    Joined:
    Oct 24, 2010
    Messages:
    6,344
    Location:
    Dunnellon, Florida
    What is the PH level??Did you recently start heating your house??
     
  12. DeeBee

    DeeBee Astrea Snail

    Joined:
    Sep 4, 2012
    Messages:
    54
    Location:
    Charlotte, NC
    That was my assumption as well. Every time I test I have used both the Salifert and Red Sea tests to validate each other. Typically there is around a 10% variance between the two with Mg but they both still register over 1300.

    Are there any factors that can give false Mag readings??? I will test it again tonight and let you know what both tests are giving me.


    I have around 60 lbs of Marco Rock (Calcium carbonate) and a 2 inch sand bed of CaribSea special grade argonite


    Yep, that will probably be the first thing I try.
     
    Last edited: Oct 20, 2014
    floydie83 likes this.