Alkalinity in reef tank is at 20 dKH

[starfishguy869]

I recently tested my reef alkalinity and saw the reading was at nearly 20 dKH. I triple checked and made sure to check my water change tank, which read a 9.8 (normal). I wanted to ask if there is a way to decrease the alkalinity at a reasonable rate. I know that concentrated hydrochloric acid works, but the stuff I have is from the hardware store and half a year old, and I was worried about heavy metals getting into my tank. I am wondering if something like vinegar would work, or something else that is cheap and easily available. I also can’t let it go down naturally as there is very little coral in the tank. If anyone can give me any help, it would be appreciated. Thank you.

 

[Mr. Mojo Rising]

How do your corals look? In what period of time did it increase from 9 to 20? If your corals are fine then I would say its a testing error.

 

[starfishguy869]

Duncans and euphyllias are looking a little closed up, so I know this is the problem. I don’t think this is a testing error.

 

[starfishguy869]

Also, nitrates and phosphates are fine

 

[Tahoe61]

Testing kit?
Salt Mix?
Have you dosed any products.
With such a notable swing, I tend to think testing error.

 

[t5Nitro]

how large is the tank? Can you easily change 50% water volume to get you back to an alkalinity around 15 for now?

Muriatic acid will lower it back down, but I don’t think I would dose it directly to a display tank. I’d almost be more inclined to do two large water changes.

Other people with more experience using an acid would have to chime in with respect to safety using it in the tank itself. Perhaps it could be a slow continuous drip or # drops or low volume mL per day slowly to get alkalinity back in shape with the starting dose depending on how much volume you’re dealing with. You’d have to keep the tank well aerated with surface agitation, skimming etc.

If you were able to do two 50% water changes you might be more likely to get to 15 and then to 12.5 fairly safely. Then, let it fall from there on its own and find the source of the problem.

 

[tripdad]

Do you have a friend or LFS nearby that can do a test to verify? I agree with a water change regimen. Use the acid to lower the new water alk BEFORE doing the water change, aerate well, then chage water.

 

[t5Nitro]

You’d want the friend or LFS to check both the wc reservoir and tank water to make the comparison more meaningful, but OP has already gotten similar results on repeat testing and comparatively different/expected results in the water change tank reservoir water. The corals clinically symptomatic, so it does make sense the test is probably not the issue.

 

[Randy Holmes-Farley Verified Community Expert]

Vinegar will not work. I suspect a test issue, but on the fluke chance it is real, I’d let it fall on its own or add sodium bisulfate very slowly. There’s a recipe thread in this forum on it.

 

[starfishguy869]

Where do you find pure sodium bisulfate? the stuff I have is from the hardware store and is only 90% NaHSO4 and the rest is filler. I also don't trust the muriatic acid from the hardware store.

I could add it into my water change tank and do 20% water changes if I have a source

 

[starfishguy869]

Also, why doesn't vinegar work?

 

[starfishguy869]

Ok I just tested it again and it was just a test error. Idk how that happened since I literally triple checked. I’m guessing my corals are looking bad cause of something else

 

[Randy Holmes-Farley Verified Community Expert]

Also, why doesn't vinegar work?

Because once it is metabolized by bacteria, all the alk returns. You need a mineral acid.

I understand you’ve solved this problem, but for other readers, here’s the bisulfate thread:

https://www.reef2reef.com/threads/s...in-new-salt-water-or-in-display-tanks.362825/

 

[breathing underwater]

Somewhat related: I recently had some issues keeping alk up above about 7.5 and my sps were looking off. Finished up a bottle of Hanna checker reagant and upon starting a new bottle got an alkalinity of 19.6!

Panic and skepticism both led me to buy two more Hanna bottles and a Salifert kit, all of which agreed that it was above 19dkh!

Apparently a wildly faulty original batch of reagent. Seriously disappointed to say the least.

I simply dosed only calcium chloride for about 2 weeks testing frequently as it floated down to 11, then started dosing alkalinity lightly to taper it down to 9. Amazingly, out of about 25 acros only lost one (red dragon) to RTN. Though several lost color and growth for a bit.

Suddenly made sense why my sandbed was seeing so much abiotic precipitation and clumping!

Lesson learned: I still use the Hanna checker but every couple weeks and especially with new bottles of reagent, and cross check with Salifert.

Best of luck with your challenges!

 

[Chicago Johnny]

Somewhat related: I recently had some issues keeping alk up above about 7.5 and my sps were looking off. Finished up a bottle of Hanna checker reagant and upon starting a new bottle got an alkalinity of 19.6!

Panic and skepticism both led me to buy two more Hanna bottles and a Salifert kit, all of which agreed that it was above 19dkh!

Apparently a wildly faulty original batch of reagent. Seriously disappointed to say the least.

I simply dosed only calcium chloride for about 2 weeks testing frequently as it floated down to 11, then started dosing alkalinity lightly to taper it down to 9. Amazingly, out of about 25 acros only lost one (red dragon) to RTN. Though several lost color and growth for a bit.

Suddenly made sense why my sandbed was seeing so much abiotic precipitation and clumping!

Lesson learned: I still use the Hanna checker but every couple weeks and especially with new bottles of reagent, and cross check with Salifert.

Best of luck with your challenges!

I also had an alkalinity issue, or it appeared to be one with a Hanna checker and their reagent. I am new to saltwater and for a couple weeks started to panic, but have 2 tanks and both were dropping alkalinity. When I got readings in the 5 range, and one tank has no fish, only rock and CUC and everyone in there looked fine I opened up my spare reagent. With the new bottle my readings were fine. The lot # in question is 2255 and expires on 08/2026. The bottle had only been opened for maybe 2 months, and was not contaminated with anything else. Do these start to go bad that fast once opened, or is there maybe a bad batch of reagent out there.

 

[rishma]

I also had an alkalinity issue, or it appeared to be one with a Hanna checker and their reagent. I am new to saltwater and for a couple weeks started to panic, but have 2 tanks and both were dropping alkalinity. When I got readings in the 5 range, and one tank has no fish, only rock and CUC and everyone in there looked fine I opened up my spare reagent. With the new bottle my readings were fine. The lot # in question is 2255 and expires on 08/2026. The bottle had only been opened for maybe 2 months, and was not contaminated with anything else. Do these start to go bad that fast once opened, or is there maybe a bad batch of reagent out there.

I keep mine in the fridge after opening. Seems to stay accurate for a couple months

 

[Randy Holmes-Farley Verified Community Expert]

I keep mine in the fridge after opening. Seems to stay accurate for a couple months

I only use Hanna HR nitrate and Hanna phosphate, but I also store mine in a fridge.