Lowering Alk using sodium bisulfate

[Randy Holmes-Farley Verified Community Expert]

A word of caution, sodium bisulfate will reduce oxygen/ph of your water. Hence not recommend as an in tank treatment.

Do you use crushed coral as substrate?

No, that is not true. It reduces pH and alk, but it has no effect on O2.

 

[Randy Holmes-Farley Verified Community Expert]

Hello Randy I’ve read your thread from many years ago about lowering the alk in newly mixed water change water using sodium bisulfate in efforts to lower tank alk. But being completely honest my brain doesn’t remotely think the way yours does so I was hoping you could dumb it down for me.

currently my tank Alk is 10.9 the salt I use is tropic Marin pro reef salt. My end goal is to get my reef system alk to around 8.5. Here are the questions I have

1. how quickly can I complete this safely. ( how many five gallon water changes)
2. How much sodium bisulfate do I add to the five gallon buckets?
3. Do you still recommend the sodium bisulfate brand from your 2018 post or is there a newer/better product you recommend?
4. When you say aerate the water to brithe ph back up, can that be done with power heads or would I need to purchase and air stone?
5.does it matter if I add the bisulfate before or after the salt?

thanks I’m advance and please let me know if there is anything important I overlooked. Have a great night.

Have you tried the alk test on your new salt water?

I think bisulfate is a great way to reduce alk in new salt water. Dropping it to 3-4 dKH and then doing some water changes with it is a good way to reduce alk in the tank.

I have not looked lately at bisulfate products, but the original recommendation should be fine.

 

[Mr.Guy83]

What alk test kit do you use? Have you tried a difference one or a new reagent.

If you have a pair of 0.01g scales ($20 Amazon) you can very easily make a alk reference solution, you then test that to see if your testing kit is reading correctly.

Yes it sounds very weird and I would not believe that is happening until you rule everything else out first, a slight increase may be possible on paper but for over 6 months, with you using 4dkh lower water when doing water changing, I would discount a natural increase.

Hanna, trident, and salifert

 

[Mr.Guy83]

Yes, this is a point I was meaning to make as it wasn’t clear from the posts if the op was meaning to lower his new salt mix or try and lower the Intank water?

Don’t try and lower the display alk with live animals in the display.

No this is strictly for the new 5gallon salt water mix prior to adding it to they system. Also plan on 24hr aeration

 

[Reef.]

Have you tried the alk test on your new salt water?

I think bisulfate is a great way to reduce alk in new salt water. Dropping it to 3-4 dKH and then doing some water changes with it is a good way to reduce alk in the tank.

I have not looked lately at bisulfate products, but the original recommendation should be fine.

Do you believe it’s possible or likely that the OP using 7dkh water to change 5 gallons of water every week for over 6 months into a 11dkh tank of 34g would result in no alk drop?

 

[Reef.]

Hanna, trident, and salifert

I’m guessing you are getting the same readings on the Hanna and Salifert?

 

[Mr.Guy83]

Have you tried the alk test on your new salt water?

I think bisulfate is a great way to reduce alk in new salt water. Dropping it to 3-4 dKH and then doing some water changes with it is a good way to reduce alk in the tank.

I have not looked lately at bisulfate products, but the original recommendation should be fine.

New salt water is around 7.8 via Hanna checker but when that water is added to the main system via WC . My alk remains the same and never falls. I’ve tested with three different brands.
Would you suggest a massive water change or using the bisulfate to lower the alk in my 5 gallon water changes until I get my tank level where I want it? (8.5)

 

[Randy Holmes-Farley Verified Community Expert]

Do you believe it’s possible or likely that the OP using 7dkh water to change 5 gallons of water every week for over 6 months into a 11dkh tank of 34g would result in no alk drop?

Maybe.

 

[Randy Holmes-Farley Verified Community Expert]

New salt water is around 7.8 via Hanna checker but when that water is added to the main system via WC . My alk remains the same and never falls. I’ve tested with three different brands.
Would you suggest a massive water change or using the bisulfate to lower the alk in my 5 gallon water changes until I get my tank level where I want it? (8.5)

I’d stick to 10-20% changes with 3-4 dKH water. PH will be an issue with larger changes. The pH even after aeration of 3 dKH water will be in the 7’s.

 

[Reef.]

Maybe.

I was worried about that reply, that’s why I added the other option of ‘likely’ :D

Lesson! never ask a scientist a question that has more than one possible answer.

 

[Mr.Guy83]

I’d stick to 10-20% changes with 3-4 dKH water. PH will be an issue with larger changes. The pH even after aeration of 3 dKH water will be in the 7’s.

It’s like I’m stuck between a rock or hard place . Stick with high dKH or deal with low pH even after aeration. How soon after adding bisulfate to my 5gallon NSW can I test the alk level? Should I does a tablespoon at a time until I get the desired result?

 

[Reef.]

It’s like I’m stuck between a rock or hard place . Stick with high dKH or deal with low pH even after aeration. How soon after adding bisulfate to my 5gallon NSW can I test the alk level? Should I does a tablespoon at a time until I get the desired result?

To give you an idea as I do this every week, I mix 25l and use 5g of Seachem acid buffer to drop alk of 11dkh to around 7, I use an air stone and power head, the ph comes back up after 1 hour, not using the air stone it took 24hours, I can test alk as soon as it’s been mixed.

I add the buffer with the salt both at the same time.

I would want to get to the bottom of your alk issue first tho, a lot of work to do this to just have your alk be an issue after.

 

[Mr.Guy83]

To give you an idea as I do this every week, I mix 25l and use 5g of Seachem acid buffer to drop alk of 11dkh to around 7, I use an air stone and power head, the ph comes back up after 1 hour, not using the air stone it took 24hours, I can test alk as soon as it’s been mixed.

I add the buffer with the salt both at the same time.

I would want to get to the bottom of your alk issue first tho, a lot of work to do this to just have your alk be an issue after.

Yea I agree, I’ve been battling for so long I honestly don’t know what else to do. My hope is I can use this method until I get my tank level to around 8.5. And then go back to just regular wc. My levels don’t move when my alk is high hopefully they won’t budged when I get them into a more acceptable range.

out of curiosity what salt do you use that mixes at 11?

 

[Reef.]

Yea I agree, I’ve been battling for so long I honestly don’t know what else to do. My hope is I can use this method until I get my tank level to around 8.5. And then go back to just regular wc. My levels don’t move when my alk is high hopefully they won’t budged when I get them into a more acceptable range.

out of curiosity what salt do you use that mixes at 11?

Instant Ocean. It is actually nearer 11.5dkh.

I previously used Tropic Marin but the cost got out of control.

 

[Randy Holmes-Farley Verified Community Expert]

It’s like I’m stuck between a rock or hard place . Stick with high dKH or deal with low pH even after aeration. How soon after adding bisulfate to my 5gallon NSW can I test the alk level? Should I does a tablespoon at a time until I get the desired result?

The alk can be tested within a few min, as soon as it disperses.

If you can get the pH of the water change water to 7.6 it should be fine for a small change.

You can add the full calculated amount at once, or go stepwise if that makes you more comfortable. You can always add back alk if you overshoot.

 

[Mr.Guy83]

The alk can be tested within a few min, as soon as it disperses.

If you can get the pH of the water change water to 7.6 it should be fine for a small change.

You can add the full calculated amount at once, or go stepwise if that makes you more comfortable. You can always add back alk if you overshoot.

So 1.2 grams per 10 Liters, drops alkalinity by 2.8 dKH.

If you do not have a scale, we can roughly estimate how much is in a teaspoon:

(That’s from your older post I just want to make sure I’m doing this correctly before I start)

So I’ll be adding bisulfate to a 5 gallon (approx 18.927L) two level teaspoons should drop the alk in the bucket by 5.6 (2.8 x2)
Last time I tested my bucket salt mix was around 7.8 which means my 5 gallon new salt water
Mix should be around 2.2dKH. If all my math is correct will adding 2.2dKh negatively affect 42 gallons of tank water at 10.9?
Will the drop be too sudden too fast or is this considered minimal?

 

[attiland]

You are going to bite my head off for this but do no water changes and leave the thing alone. If you have coral it should drop naturally. If no coral yet it doesn’t matter. It works as long as you don’t dose anything increasing alk.

on the other hand I had issue with Hanna alk tester when I had a wrong batch of argent. Try a new battle if you have one by hand. Change batteries too.

by the way depending on salt the fresh mix alk is pointer only rather than exact number at least this is my experience with blue bucket Red Sea. It can change as much as 0.2 in my case in a day. Since I dose all for reef my alk changes take 2-3 days anyway.

 

[Acros]

Unless you isolate the origin of this alk spike, sodium bisulfate is only a temporary solution.

 

[Randy Holmes-Farley Verified Community Expert]

Unless you isolate the origin of this alk spike, sodium bisulfate is only a temporary solution.

Nearly everything we do in a reef tank is a temporary solution, that needs to be repeated periodically.

Knowing the cause often does not provide a solution. Folks with low demand tanks do see alk rises and it is likely from sand and rock dissolution.

Is that the case here? Only time will tell if it needs repeating.

 

[Acros]

Nearly everything we do in a reef tank is a temporary solution, that needs to be repeated periodically.

Knowing the cause often does not provide a solution. Folks with low demand tanks do see alk rises and it is likely from sand and rock dissolution.

Is that the case here? Only time will tell if it needs repeating.

I was under the impression that rock would leach/produce alk only under a certain ph.