Lowering alk in water change water?

[Fishfreak2009]

How do I lower my alkalinity down in fresh mixed seawater? I have a 75 gallon reef and I normally do 10 gallon water changes once every 1-2 weeks. Originally, the tank sat at an alk level of around 11.5, but we let it naturally lower to around 9.3 as the corals and clams have been growing, and maintained it there with dosing alk. Alk was tested from the display the day before the last water change and was at 9.3. After the water change, the alkalinity swung up. I hadn't even thought of it, as I haven't had issues before, but the next morning, the alk was at 11 in the display and 2 Acropora completely RTNd. It has now been 4 days and 1 more Acropora has completely RTNd, and 2 lost about half their flesh, and our Hippopus clam died. We fragged the half gone Acropora off the dead skeleton and remounted them, and they've lost no other tissue now.

Alk is now back down to 9.3. Using reef crystals salt. All the rest of the corals, including the 30+ other Acropora seem none the worse for wear (still opening their polyps etc).

Everything else in the tank has stayed stable for the past few months. Calcium maintains between 435 and 455, and magnesium is always around 1500. Nitrates are 25ppm, and phosphate is high (leaching from rocks) at 0.5ppm, but doesn't seem to bother the corals.

We use well water and Reef Crystals for all our water changes.

Basically, how do I lower the high Alk in the freshly mixed reef crystals water before I add it to the tank?

 

[RobB'z Reef]

I believe vinegar would reduce it, as would any acid such as hcl (like muratic). However, that being said I seriously doubt it was your water change. If you only changed 13% of your water and I don't know what reef crystals runs at but at worst if it's 11 that's only going to raise your Alk by .22 at most. You might not even be able to reliably measure that. Now if you did it frequently enough it might gradually raise it to that level after months.

 

[Randy Holmes-Farley Verified Community Expert]

Sodium Bisulfate to Reduce Alkalinity in New Salt Water or in Display Tanks

I just want to record these calculations in their own thread to refer back to in other threads. When alkalinity is too high in new salt water or in a display tank, acid can be used to lower the alkalinity. You can easily use muriatic acid (hydrochloric acid), or sodium bifulfate (e.g...

www.reef2reef.com

Muriatic acid?

Can I use this to lower ALK in freshly mixed saltwater.? Do I just add a little bit at a time and test until it gets to the level I would like it?

www.reef2reef.com

 

[Fishfreak2009]

I believe vinegar would reduce it, as would any acid such as hcl (like muratic). However, that being said I seriously doubt it was your water change. If you only changed 13% of your water and I don't know what reef crystals runs at but at worst if it's 11 that's only going to raise your Alk by .22 at most. You might not even be able to reliably measure that. Now if you did it frequently enough it might gradually raise it to that level after months.

Reef crystals mixes at an alk around 13. No other changes in the tank, and for it to happen immediately after water change, where all other parameters are the same, I can't think of anything else.

 

[Randy Holmes-Farley Verified Community Expert]

I believe vinegar would reduce it, as would any acid such as hcl (like muratic). However, that being said I seriously doubt it was your water change. If you only changed 13% of your water and I don't know what reef crystals runs at but at worst if it's 11 that's only going to raise your Alk by .22 at most. You might not even be able to reliably measure that. Now if you did it frequently enough it might gradually raise it to that level after months.

No, vinegar will not accomplish permanent alk lowering.

 

[RobB'z Reef]

No, vinegar will not accomplish permanent alk lowering.

Hmmm, thanks for the correction! My bad.

 

[Fishfreak2009]

Well, I tested the alkalinity in a 5 gallon bucket mixed about 5 hours ago and the alkalinity is over 15. So not sure if I have a bad bag now...

Update: tested our well water and the alkalinity straight from the faucet is 11.5 dKH.

 

[RobB'z Reef]

Reef crystals mixes at an alk around 13. No other changes in the tank, and for it to happen immediately after water change, where all other parameters are the same, I can't think of anything else.

So by my rough math, the Delta is 3.7 of which 13% should raise it roughly .5. how frequently do you measure your alk and with what?

 

[Fishfreak2009]

Update: tested our well water and the alkalinity straight from the faucet is 11.5 dKH. So not sure where to go from here. Thinking I'll need to lower the alk in the well water, then mix the reef crystals, then lower alk again in the saltwater?

I guess it explains why we rarely have to dose alk/calcium. The well water we've been topping off with has been buffering this whole time.

@Randy Holmes-Farley does this sound like an appropriate plan of action?

 

[Fishfreak2009]

So by my rough math, the Delta is 3.7 of which 13% should raise it roughly .5. how frequently do you measure your alk and with what?

I measure alk at least every couple days to every day (went back up to daily since this happened) with the Salifert alkalinity test kit.

Apparently I'm using salt with high alk and tap water with high alk, and the combo of the 2 is just pushing my alk way too high.

 

[gbroadbridge]

How do I lower my alkalinity down in fresh mixed seawater? I have a 75 gallon reef and I normally do 10 gallon water changes once every 1-2 weeks. Originally, the tank sat at an alk level of around 11.5, but we let it naturally lower to around 9.3 as the corals and clams have been growing, and maintained it there with dosing alk. Alk was tested from the display the day before the last water change and was at 9.3. After the water change, the alkalinity swung up. I hadn't even thought of it, as I haven't had issues before, but the next morning, the alk was at 11 in the display and 2 Acropora completely RTNd. It has now been 4 days and 1 more Acropora has completely RTNd, and 2 lost about half their flesh, and our Hippopus clam died. We fragged the half gone Acropora off the dead skeleton and remounted them, and they've lost no other tissue now.

Alk is now back down to 9.3. Using reef crystals salt. All the rest of the corals, including the 30+ other Acropora seem none the worse for wear (still opening their polyps etc).

Everything else in the tank has stayed stable for the past few months. Calcium maintains between 435 and 455, and magnesium is always around 1500. Nitrates are 25ppm, and phosphate is high (leaching from rocks) at 0.5ppm, but doesn't seem to bother the corals.

We use well water and Reef Crystals for all our water changes.

Basically, how do I lower the high Alk in the freshly mixed reef crystals water before I add it to the tank?

Muriatic Acid is how I do it.

If you wish to drop 2dkh in 10 gal you would add about 2.4ml of 30% muriatic acid to the freshly mixed salt water and aerate well for 48 hours or so to drive off the CO2 produced.

Don't add to the tank until the pH has stabilised.

 

[Randy Holmes-Farley Verified Community Expert]

Update: tested our well water and the alkalinity straight from the faucet is 11.5 dKH. So not sure where to go from here. Thinking I'll need to lower the alk in the well water, then mix the reef crystals, then lower alk again in the saltwater?

I guess it explains why we rarely have to dose alk/calcium. The well water we've been topping off with has been buffering this whole time.

@Randy Holmes-Farley does this sound like an appropriate plan of action?

Lowering the alk sounds like a good plan. I give some recipes above.

 

[Fishfreak2009]

Lowering the alk sounds like a good plan. I give some recipes above.

I'm going to follow the first recipe. Just did the math, will be ordering the biosulphate

 

[Randy Holmes-Farley Verified Community Expert]

I'm going to follow the first recipe. Just did the math, will be ordering the biosulphate

Lets us know how it works for you!