Alkilinity high and not going down

[ALowCountryReef]

I will try to give all available info if anyone can possibly help.

I am running a low nutrient (not ultra-low) system so 8.4-8.6 is high alkilinity
My new seawater reads 7 DKH.
Tank reads 8.4-8.6
Calcium is being slowly consumed.
Started tank with Pukani and sand (not live)
75 gallon water volume
Yes, I got a new test kit, tried an alternative brand, and had both waters tested at LFS so numbers are
true.
Nitrates 0, phospates are 0, but I do get light algae growth that is maintained by cleanup crew and a glass clean twice a week do there are nutrients in the tank.

As I stated my alkilinity stays consistent at 8.4-8.6 without alk additions. Calcium is being used although slowly. Mainly frags of SPS (about 5 of them). They are colored up nicely and have decent polyp extension but are not forming bases (in tank for 2 months now). Tip growth is happening but very slowly. I'm guessing both of these are due to high alk for a low nutrient tank. I do 5-10 gallon water changes weekly with my new sea water and it does not affect alk. This past weekend changed out 20 gallons (75 gallon true total system volume)hoping to bring it down but it didn't budge. What is sustaining alkilinity and how can I bring it down?

 

[Randy Holmes-Farley Verified Community Expert]

Can you list any additives you are using, if any, including the calcium additive?

What do you use to replace evaporation?

The slow growth may be because it is a ULNS situation.

 

[ALowCountryReef]

Thanks for the reply. Have run Zeovit for a year and didn't have any issues until I added 7 chromis in September. Nitrates and Phosphates rose moderately and then zeroed back out within 2 weeks. Corals brightened up considerably (one of the main reasons for adding more fish was for more input) but alkilinity also raised over that same period. I test every other day and stopped dosing alk after a couple days. It continued to rise on it's own until becoming stable at 8.4-6. Calcium additions have cut 90%.

Additives
Zeobak (bacteria), Zeostart (carbon source), Amino acids 3 times weekly, K balance (potassium), Coralvit and Zeofood (coral and bacteria food), iodine sparingly, 3 part BRS although Magnesium stays constant and has never been added. Evaporation is replaced using 6 stage RO/DI from BRS, TDS meter reads zero, all replacements done timely. I understand low growth may come with ULNS although I am definitely not UL just L. Before the addition of fish, frags were growing bases and tips but colors were very drab. Alk was being mantained at about 7.5 and constant dosing to keep levels stable. When alkilinity spiked, bases receded slightly but then stopped when it leveled at the higher 8.4-6. Colors boomed after and have never looked better. I'm sure growth would come back once alk can be reduced but can't for the life of me understand what is keeping it up and stable where it is.

 

[Randy Holmes-Farley Verified Community Expert]

I do not know how zeostart and the amino acids are formulated, but some logical ways of doing it will add alkalinity.

 

[ALowCountryReef]

HAHA! isn't that the joke, nobody knows how they are formulated. Zeostart is carbon dosing and it pretty much smells like vinegar. I will obviously need to keep dosing it to keep my filtration going since I have no other filtration in the sump. I have used the same dosing regimen of Zeostart since the beginning so I would be surprised if that was the culprit. I think I will stop dosing of all other additives except zeobak and start, and Calc, Alk, Mag and see if that makes any positive changes. Thank you very much for the help and let me know if anything else comes to mind.

 

[Randy Holmes-Farley Verified Community Expert]

HAHA! isn't that the joke, nobody knows how they are formulated. Zeostart is carbon dosing and it pretty much smells like vinegar. I will obviously need to keep dosing it to keep my filtration going since I have no other filtration in the sump. I have used the same dosing regimen of Zeostart since the beginning so I would be surprised if that was the culprit. I think I will stop dosing of all other additives except zeobak and start, and Calc, Alk, Mag and see if that makes any positive changes. Thank you very much for the help and let me know if anything else comes to mind.

Vinegar (acetic acid) can be formulated as sodium acetate (with no sudden pH drop, but it adds alk) or as normal acetic acid (at low pH like vinegar, which will not impact alkalinity).

 

[ALowCountryReef]

Thank you for the knowledge. I appreciate your help!

 

[Randy Holmes-Farley Verified Community Expert]

You're welcome.

Let as know if you find the cause.

 

[ALowCountryReef]

OK @Randy Holmes-Farley , I have found that my Zeovit media change schedule is the culprit. I have found that after six weeks the alkilinity starts to rise on it's own. As soon as the media is changed, it slowly starts to fall over the next week. Then I have to add 2 part again. 6 weeks is the minimum time for change, i was going 8-10 weeks. I will watch over the next few 6 week periods and monitor but I have seen this happen now over 3 media changes. Chime in if you know why this may be the case. Thank you again for your help, just wanted to give an update.

 

[Randy Holmes-Farley Verified Community Expert]

Just to clarify, you think the new media lowers alk then stops lowering it, or after a few weeks in the tank, the media is raising it?

You are talking about the zeolite material, right?

 

[ALowCountryReef]

I don't think it is the media directly. From my humble observations since November, I see Alk begin to rise after six weeks of running the media. It will climb from 7.5 to 8.2 over a week even though all Alk and Calc are stopped dosing at that point. If the media is changed at the end of week 7, The Alk will drop back down to 7.5 in about 4-5 days and dosing of Alk must be resumed but Calc stays slightly elevated for about 2 weeks. If I change the media at the end of 6 weeks. Alk and Calc do not rise and dosing is continued as regularly scheduled. What is happening is definitely above my paygrade of understanding and seems strange to me, but thought I would share. As I stated earlier this has been over three changes.
Thanks for your time!

 

[Randy Holmes-Farley Verified Community Expert]

I'm not actually sure what, if anything, zeovit media accomplishes besides being a good place for bacteria to grow. Maybe replacing it (and adding back media with no bacteria) is changing the denitrification taking place in the tank, which can impact alkalinity.