Rising dKH mystery.

[Evan West]

Hello all, My dKH is up to 14 and im not sure why. When I mix fresh saltwater with RO water and IO Reef Crystals the dKH is 12 so it has gone up by 2! My tank is cycling so I have not dosed anything or done any water changes. All I have done is top off the tank with fresh RO water. Any idea why my dKH is rising? Could the RO water I have been using to top off my tank with have a high alk and be causing the rise?

 

[Elementalj]

Hello all, My dKH is up to 14 and im not sure why. When I mix fresh saltwater with RO water and IO Reef Crystals the dKH is 12 so it has gone up by 2! My tank is cycling so I have not dosed anything or done any water changes. All I have done is top off the tank with fresh RO water. Any idea why my dKH is rising? Could the RO water I have been using to top off my tank with have a high alk and be causing the rise?

I'd leave it be. It will probably regulate itself soon.

 

[Randy Holmes-Farley Verified Community Expert]

It doesn't rise on its own, but at this point it is likely reflecting the salt mix, even if the measurement is seemingly different.

Denitrification boosts alk, but nitrification lowers it by the same amount, so the nitrogen cycle is not likely causing any rise.

Fine suspended calcium carbonate in the water will show as false high alk, so be sure it is settled and clear before any testing.

 

[Elementalj]

 

[Evan West]

It doesn't rise on its own, but at this point it is likely reflecting the salt mix, even if the measurement is seemingly different.

Denitrification boosts alk, but nitrification lowers it by the same amount, so the nitrogen cycle is not likely causing any rise.

Fine suspended calcium carbonate in the water will show as false high alk, so be sure it is settled and clear before any testing.

Tank is a week or more into the cycle so its settled and clear by now. My other theory is a long shot but there are lots of dead tube worm tubes on my rock, could the calcium from those as they dissolve and erode cause this rise?

 

[Elementalj]

If accompanied by low low pH then things could dissolve. But in the face of high alkalinity? I'm not sure.

 

[Elementalj]

Just hang for a bit. It should equalize soon. I'd add some aeration or surface agitation to the equation and see if that helps.

 

[Evan West]

Just hang for a bit. It should equalize soon. I'd add some aeration or surface agitation to the equation and see if that helps.

I have a ph of 7.8-8 so I dont think so, ill do some WC as soon as I can I guess and see how it goes.

 

[Randy Holmes-Farley Verified Community Expert]

Calcium carbonate tubes won't be dissolving into the water if the alk is normal and the pH is 7.8 or above.

FWIW, aeration won't alter total alkalinity, only pH.

 

[Elementalj]

Low pH and high alkalinity is an indication of excess co2 in the surrounding atmosphere. I'd say add some aeration. And let it equalize.

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, there's no need to be concerned about 14 dKH alkalinity at this stage.

 

[Elementalj]

Agreed.

 

[Randy Holmes-Farley Verified Community Expert]

Low pH and high alkalinity is an indication of excess co2 in the surrounding atmosphere. I'd say add some aeration. And let it equalize.

That will change the pH, not the alkalinity.

 

[Elementalj]

Understood.

 

[Evan West]

FWIW, there's no need to be concerned about 14 dKH alkalinity at this stage.

So am I to assume that at some point it is a concern and that at some point it should drop?

 

[Randy Holmes-Farley Verified Community Expert]

So am I to assume that at some point it is a concern and that at some point it should drop?

It would be a big concern if you had hard corals in an ultra low nutrient system, but in general it won't be a problem because growing corals will quickly bring it down.

 

[choss]

Evan,

I had the same problem when I first set up my tank. I couldn't for the life of me figure out why it was so high. Then I tested a fresh mix of salt water and it was off the charts. I was using Reef Crystals. I switched salt and problem solved. Originally I went Oceanic and now and using Tropic Marin Pro. But problem was solved.

 

[Elementalj]

Ok, so I just ordered a box of tropic Marin. Been using reef crystals for friggin YEARS

 

[GainesvilleReef]

If you don't like the high dKH switch salts to a "non-reef" type. I had a problem mixing the "reef" salts consistently. If I had a good batch it would be as high as 14. Maybe you got some high batches. But like Randy said, it's not a big issue. In the past I have added a few montiporas to pull down the initially high alk. They seem hardy enough to deal with the high alk. I am actually starting a new tank now. I have reduced the alk of all the new water to 8 with HCL.

 

[Evan West]

If you don't like the high dKH switch salts to a "non-reef" type. I had a problem mixing the "reef" salts consistently. If I had a good batch it would be as high as 14. Maybe you got some high batches. But like Randy said, it's not a big issue. In the past I have added a few montiporas to pull down the initially high alk. They seem hardy enough to deal with the high alk. I am actually starting a new tank now. I have reduced the alk of all the new water to 8 with HCL.

I plan to keep LPS and softies so from my understanding they should tolerate it well, that said I plan to switch to Read Sea or MW-Marinemix soon. I dont personally care about the high alk as long as it wont harm my corals once I add them, I want optimal conditions so if the alk being high is an issue I want to correct it.