ALK Up and Down....

Reef Pets · May 13, 2009

For the past 3-4 months I have had a serious issue will keeping ALK at the proper lever. I am able to keep MAG at about 1300 and Calcuim at roughly 450. But when it come to ALK it will lower about 3 points every other day. For example I checked it yesterday mid-day and the ALK was at 9 and today its at 6. About every other day it does this. I have tried many different test kits with the same results. Also, I have tried the Baking Soda method, Kents dkh, sodium ash and so one.
I use to have some of the best SPS ever and now the colors are good for a little while and they the colors dull and then they are good again...
I just cant seem to beat this problem and I really dont trust calcium reactors enough to add one to the system. Any idea would be helpful.

Test kit - API

Tank Specs:
Roughly 400 gallons
20 gallons of Chaeto
All 20K Metal Halides
Skimmer - Euro Reef CS12-2
Mixture of softies, LPS and SPS (vendors mixture)
Calcium - 450
ALK - who knows, thats the problem
Mag - 1300
PH - 8.1
Nitrates - 0
Phosphate -0

roshi719 · May 13, 2009

Gary what is your dosing schedule like?

Reef Pets · May 13, 2009

Typicaly I dose everyday. I have been using 2 part from Bulk Reef Supply and have got the dosing of Mag and Calcuim down to a science to keep those two stable. I have tried dosin even twice a day on ALK and no stability has come from it.

roshi719 · May 13, 2009

I know on my display at home, my alk was low and swinging, and I was dosing like crazy and it wouldn't stabilize. I did 20% water changes twice a week for two weeks and it stabilized. I know it sucks doing that much water change on a big system, but maybe that would help. The way I understand it is that water, even saltwater, can have only so much TDS in it. Once that level is reached then it is a give and take between ions. For instance if you want more calcium and the TDS is at saturation then some other ion has to give up it's place and precipitate out for the calcium to go in. Since all of the two parts out there are salt based, that means we are putting in two ions and only one gets used up. For instance CaCl, calcium Chloride, the calcium gets used up, but the chloride ion stays in solution and over time the levels accumulate.

I deal with pools and hottubs at my other job, and it is the same thing over there. If the TDS is too high in a spa all you can do is drain it and start over. You can add all the chemicals you want and it will never balance.

I hope my rant makes some sense to you.:nerd:

Reef Pets · May 13, 2009

Rant? Thats great information and makes plenty of since. It does suck doing all of those water changes but its more frustating not to have the tank stable and pitching money away on additives to bring the ALK to its proper level.
I have tried everything else that I know of, so off to water changing I go.
Thanks for the help.