Low alk

[bighead]

I have a 90'gal with 40 breeders sump up and running for over 2 years with no problems my par are
Alk 7.8
Cal 440-450
Mag 1320
Ph 8.2-8.4
Temp 78
My alk dropped to 6.4 and I am having a hard time raising it I have and always use baking soda all other levels are good I use Red Sea pro salt and red sea test kits I have tested many times same results all the time
I have mostly sps and a large hammer coral and a clam believe it or not all coral looks pretty good but the clam
This has been going on for about 3 weeks now I just changed 25 gal of water and no change
Any suggestions on fixing this

 

[hkgar]

You listed Alk as 7.8 but wrote that it dropped to 6.4. What is it now? How often do you test Alk? That big a drop in 24 hours would likely be a testing error, over a few days not really a big drop per day. With SPS you need to maintain stable ALK and if it gets to low do not bring it rapidly. If mine gets low and bring it up about .3 per day. Doesn't happen often as I us a calcium reactor.

Here is a link to a dose calculator for Alk, Ca and Mag.

http://reef.diesyst.com/chemcalc/chemcalc.html

The numbers you listed are fine for your tank.

 

[bighead]

My alk has dropped over 3 weeks time started at 7.8 ended at 6.4 I have been adding baking soda and it has not been going up

 

[Potatohead]

Have you verified with another test kit?

 

[bighead]

No I haven't

 

[NeilFox]

Nice link HKgar. Thanks for posting!

 

[NeilFox]

bighead, do you have a LFS that you can bring a sample to for testing?

 

[Potatohead]

No I haven't

I probably would before doing anything else

 

[bighead]

I can do that

 

[hkgar]

A drop of 1.4 over 21 days is relatively small - a usage of .06 dKh per day. You should only need to add about .1 tsp of baking soda - dissolved in either ro/di or tank water before adding - to make up that loss.

 

[hkgar]

Start doing some research regarding dosing in the Reef Chemistry forum.