Low alkalinity

[pegasus]

I posted awhile back that I am having to dose more alkalinity than calcium. I've always been under the impression that once calcium and alkalinity levels were where you want them to be, equal dosing of Alk and Cal were all that is needed to maintain levels. However, I am having to dose nearly 3x alkalinity to maintain a constant level. I've finally dialed in my dosage... 30mL of Calcium daily, and 80mL Alkalinity. I'm using BRS 2-part Alk and Cal. I opted for Soda Ash, as it keeps my pH where I want it. I mixed each mixture exactly as directed, and have been trying to get my Alk to 8.0 dKH. It doesn't seem to matter how much I add. I never goes above 7.3 dKH, and after 24 hours, it's usually 6.7 - 7.0 dKH. I use Salifert to test, and today I used the 6.7 test sample that came with the kit to check for accuracy. It was dead on. Magnesium is 1380, Calcium is 460, and pH is 8.4. Using the BRS calculator, I enter my current Alk level (7.3 dKH), and my desired level of 8.0 dKH. It recommends 75 mL of Soda Ash mixture, so I add 80 mL. I checked the level the next evening, and it's still 7.3 dKH. I have gone as far as adding 90 mL in a single dose, and it always results is no more than 7.3 dKH.

I have a 125 gallon tank, a 40 gallon tank, a 30 gallon refugium, and these are all on the same "shared" system. The 125 has roughly 125 lbs of rock and 125 lbs of sand. The 40 has 40lbs of rock and 60 lbs of sand. The refugium holds 15-20 gallons of water when running. Allowing for displacement from the rocks and sand, I'm estimating there's roughly 150 gallons of water volume in the combined systems. BRS recommends not to raise Alk more than 1.2 dKH daily, but I have no idea of how much Alk it would take to raise it that much. Half a gallon??? I just find it strange that I am having to dose in a 3:1 ratio. Anyone else having this issue?

 

[bang guy]

What is your Salinity and water temperature?

Why do you want the Calcium so high?

 

[bang guy]

On other off the wall question - can you describe how you dose your tank for me. I need excruciating detail.

 

[pegasus]

What is your Salinity and water temperature?

Why do you want the Calcium so high?

Salinity is 1.205, and temp is 80F. I didn't intend for calcium to get quite that high. My target is 425-450 ppm, but I overshot just a tad a couple of days ago. It was 490 ppm the day before, so I didn't dose yesterday. It dropped 30ppm (to 460) in 24 hours, so I'm pretty certain 30 mL will maintain it once it falls within range.

On other off the wall question - can you describe how you dose your tank for me. I need excruciating detail.

I am dosing manually ATM, as I've been working out the proper dosage... before I hook up my dosing pump. I thought it would be easier to dial it in using a graduated measuring cup rather than changing settings on the doser every day. I dose calcium midday, and alkalinity two or three hours after lights out to avoid pH overshoot. I dose in my refugium directly in front of the return pumps. The calcium goes directly into the return chamber, but I always mix the alk with a quart of tank water to pre-dilute it before trickling it into the return chamber. This seems to be the best location, as the flow in the return chamber helps mix/dilute it with the water before entering the return pumps. The pumps further blend the elements with the water before dispersing it in the tanks. As it enters through the return lines in the middle of each tank, four power heads in each tank completes the dispersion. I don't know if that's enough excruciating detail, but it was excruciating trying to type it... lol!

 

[pegasus]

PS: There are days when I miss the midday calcium dosing, so I have to do it later in the evening. On those days, I never dose the calcium and alkalinity less than an hour apart...

 

[mandy111]

I dose more alk than cal too......I think it all depends on the corals you are keeping. Since adding 3 clams i have also almost doubled my mag dosing to stay consistent. The rule of thumb i have heard is you will drop 2.8 dkh alk to every 50 ppm cal. Do you keep corals ?
This is a rough guide only, once again it depends on the corals, their growth and coarline algae can play havoc as well. Equal dosing works well for smaller systems, but once you get to your size with corals it varies considerably.
If your not keeping corals I would question your test kit, because it seems like an awful lot of alk daily if corals arnt using it.
I wouldn't worry too much, as long as numbers are within range, stability is the key, you dont want continues swings.

 

[bang guy]

How did you test your salinity? You actually gave me a really high specific gravity reading which I will assume is a typo. I'll assume your water reads S.G. of 1.025. Is that right?


Here is my suggestion:

1 - Instead of using only soda ash, mix it with baking soda. 1/3 baking soda 2/3rds soda ask.

2 - Instead of mixing your ALK additive with tank water, mix it with your topoff water and use that mixture to topoff. If you have an ATO directly connected to your DI then just use a gallon of DI water and drip it in over an hour or so instead of slowly pouring it into a high flow area.

3 - Let calcium drop below 420ppm and use 400 - 420 as your new desired range.

 

[lmforbis]

I also add more alk than calcium and way more mag than anything at least by volume, haven't calculated out molarity. I use the same 2 part you use.
You start at 7.3 add sodium carbonate to bring it up to 8 and 24 hours later it is back to 7.3. That seems normal. Your system is using 0.7 dKH every day. You bring it up then it falls. The next day you bring it back up and it falls again. Maybe you want your 24 hour later dKH to be at 8 then you would need to bring it up to 8.7 dKH when you dose. Or use a pump to gradually add it over the day. You'd still have to get it where you want it to be first then start the pump.

 

[pegasus]

How did you test your salinity? You actually gave me a really high specific gravity reading which I will assume is a typo. I'll assume your water reads S.G. of 1.025. Is that right?


Here is my suggestion:

1 - Instead of using only soda ask, mix it with baking soda. 1/3 baking soda 2/3rds soda ask.

2 - Instead of mixing your ALK additive with tank water, mix it with your topoff water and use that mixture to topoff. If you have an ATO directly connected to your DI then just use a gallon of DI water and drip it in over an hour or so instead of slowly pouring it into a high flow area.

3 - Let calcium drop below 420ppm and use 400 - 420 as your new desired range.

Yes, that was a typo... it's 1.025 SG.

1 - I'll have to try mixing baking soda in my next batch. Soda ash gives a temporary spike in pH, and baking soda gives a temporary reduction in pH, so it should balance out with the blend of the two.

2 - I have my ATO attached to my RO/DI. Instead of adding the alkalinity directly to the tanks in front of a power head as the BRS video suggests, I use the refugium as a method to deliver it to both tanks in fairly equal proportions. I've been working on raising my salinity to 1.026 SG by adding a gallon of saltwater to the refugium daily, so adding a gallon of RO water with alk in it daily will have me going in the opposite direction, wouldn't it? Not saying it's a bad idea, but it's on the opposite end of the spectrum from what I'm trying to achieve...

3 - I suppose I should have done more research to see what NSW calcium levels are. The second to last line of the instructions that comes with the Salifert CA Profi Test states: Natural sea water contains 425-450 ppm calcium. That's what I've been basing my target range on. According to http://www.advancedaquarist.com/2002/3/chemistry, "Calcium is one of the major ions in seawater. It is present in seawater at about 410 ppm the world over, so it comprises just under 1.2% by weight of the solids." That would put your suggested range of 400-420 spot on. Since an over abundance of calcium causes a reduction in alkalinity (and vice versa), it makes sense that alk levels never reached my target. What I'm having trouble wrapping my head around is why the imbalance of dosing (3:1) didn't drive down the calcium level. Oh well, I'll let calcium fall to the 410 range, and see how alk works out from there. Thanks for the heads up, BG!

I also add more alk than calcium and way more mag than anything at least by volume, haven't calculated out molarity. I use the same 2 part you use.
You start at 7.3 add sodium carbonate to bring it up to 8 and 24 hours later it is back to 7.3. That seems normal. Your system is using 0.7 dKH every day. You bring it up then it falls. The next day you bring it back up and it falls again. Maybe you want your 24 hour later dKH to be at 8 then you would need to bring it up to 8.7 dKH when you dose. Or use a pump to gradually add it over the day. You'd still have to get it where you want it to be first then start the pump.

That's the weird part... I've tested from 1 hour after dosing, to 24 hours after dosing, and it never goes above 7.3. It typically falls to 6.7 after 24 hours. I want my average to be 8.0, which means it'll have to be more than 8.0 initially, and below 8.0 before the next dose. I get that. What I'm not getting is my level ever going above 7.3. I can dose 50mL, or I can dose 100mL, and it's never more than 7.3. Yeah... it's like that.

What I'm finding (extremely) weird is that you're dosing more magnesium than anything else. I rarely dose mag, and my levels are always high. At best, I may dose 50ml mag per month. I'm using Kent TechM, as I picked up a few gallons at a great price. If you're using the powdered mix, it's possible that you may have mixed it at the wrong ratio. I'm beginning to wonder if I didn't do just that when I mixed my alk and calcium. We're only human... born to make mistakes.

 

[bang guy]

Raising Salinity is a separate issue from your Alkalinity maintenance.

To raise Salinity, I agree, just use saltwater for topoff for a day or two. It really shouldn't be a long term issue.

We need to tackle things one item at a time. The item my suggestions target is Alkalinity stability. I believe what is happening is that by using straight Carbonate (Soda Ash) you are temporarily raising the PH. Higher PH will also reduce Carbonate. By keeping the PH more stable I think you will be able to raise your Alkalinity, finally, to 8 dKH.

As a side benefit I think your Calcium will also drop less.

Try my suggestions for a week and let me know the results. I have a plan B if needed.

 

[mandy111]

Yes, that was a typo... it's 1.025 SG.

1 - I'll have to try mixing baking soda in my next batch. Soda ash gives a temporary spike in pH, and baking soda gives a temporary reduction in pH, so it should balance out with the blend of the two.

2 - I have my ATO attached to my RO/DI. Instead of adding the alkalinity directly to the tanks in front of a power head as the BRS video suggests, I use the refugium as a method to deliver it to both tanks in fairly equal proportions. I've been working on raising my salinity to 1.026 SG by adding a gallon of saltwater to the refugium daily, so adding a gallon of RO water with alk in it daily will have me going in the opposite direction, wouldn't it? Not saying it's a bad idea, but it's on the opposite end of the spectrum from what I'm trying to achieve...

3 - I suppose I should have done more research to see what NSW calcium levels are. The second to last line of the instructions that comes with the Salifert CA Profi Test states: Natural sea water contains 425-450 ppm calcium. That's what I've been basing my target range on. According to http://www.advancedaquarist.com/2002/3/chemistry, "Calcium is one of the major ions in seawater. It is present in seawater at about 410 ppm the world over, so it comprises just under 1.2% by weight of the solids." That would put your suggested range of 400-420 spot on. Since an over abundance of calcium causes a reduction in alkalinity (and vice versa), it makes sense that alk levels never reached my target. What I'm having trouble wrapping my head around is why the imbalance of dosing (3:1) didn't drive down the calcium level. Oh well, I'll let calcium fall to the 410 range, and see how alk works out from there. Thanks for the heads up, BG!


That's the weird part... I've tested from 1 hour after dosing, to 24 hours after dosing, and it never goes above 7.3. It typically falls to 6.7 after 24 hours. I want my average to be 8.0, which means it'll have to be more than 8.0 initially, and below 8.0 before the next dose. I get that. What I'm not getting is my level ever going above 7.3. I can dose 50mL, or I can dose 100mL, and it's never more than 7.3. Yeah... it's like that.

What I'm finding (extremely) weird is that you're dosing more magnesium than anything else. I rarely dose mag, and my levels are always high. At best, I may dose 50ml mag per month. I'm using Kent TechM, as I picked up a few gallons at a great price. If you're using the powdered mix, it's possible that you may have mixed it at the wrong ratio. I'm beginning to wonder if I didn't do just that when I mixed my alk and calcium. We're only human... born to make mistakes.

hi, I think @bang guy has hit the nail on the head. try what he says for a week and see.
As far as my mag goes, I am still dosing more alk and cal than mag, just my mag usage tripled since adding clams. I still dose way less mag than both the others.
Good luck with it, i will be following.

 

[pegasus]

Raising Salinity is a separate issue from your Alkalinity maintenance.

To raise Salinity, I agree, just use saltwater for topoff for a day or two. It really shouldn't be a long term issue.

We need to tackle things one item at a time. The item my suggestions target is Alkalinity stability. I believe what is happening is that by using straight Carbonate (Soda Ash) you are temporarily raising the PH. Higher PH will also reduce Carbonate. By keeping the PH more stable I think you will be able to raise your Alkalinity, finally, to 8 dKH.

As a side benefit I think your Calcium will also drop less.

Try my suggestions for a week and let me know the results. I have a plan B if needed.

Raising salinity has been a separate goal from raising alkalinity from the beginning. The purpose of raising salinity is to be sure other minor elements are readily available. As slowly as I've been raising it, it shouldn't have any bearing on the alkalinity issue. I'm at 1.025, so I'm very close to being done with that project.

I know that a lot of foreign baking soda has borate in it, but if I'm correct, American baking soda doesn't. Not that my tank could use a good cleaning, but I'd rather not use a cleanser in the process... lol! As far as baking soda goes, will Arm & Hammer baking soda be okay?

hi, I think @bang guy has hit the nail on the head. try what he says for a week and see.
As far as my mag goes, I am still dosing more alk and cal than mag, just my mag usage tripled since adding clams. I still dose way less mag than both the others.
Good luck with it, i will be following.

Thanks, Mandy. As luck would have it, I ran out of reagent for my alk and cal test kits. I ordered a Hannah Checker for alk and cal, but they won't be here until later on this week. In the meantime, I'm worried about my alk getting too low. I'll stop dosing calcium until my testers get here, but just to be on the safe side, I'll continue to dose alkalinity.

 

[lmforbis]

Yes, that was a typo... it's 1.025 SG.

1 - I'll have to try mixing baking soda in my next batch. Soda ash gives a temporary spike in pH, and baking soda gives a temporary reduction in pH, so it should balance out with the blend of the two.

2 - I have my ATO attached to my RO/DI. Instead of adding the alkalinity directly to the tanks in front of a power head as the BRS video suggests, I use the refugium as a method to deliver it to both tanks in fairly equal proportions. I've been working on raising my salinity to 1.026 SG by adding a gallon of saltwater to the refugium daily, so adding a gallon of RO water with alk in it daily will have me going in the opposite direction, wouldn't it? Not saying it's a bad idea, but it's on the opposite end of the spectrum from what I'm trying to achieve...

3 - I suppose I should have done more research to see what NSW calcium levels are. The second to last line of the instructions that comes with the Salifert CA Profi Test states: Natural sea water contains 425-450 ppm calcium. That's what I've been basing my target range on. According to http://www.advancedaquarist.com/2002/3/chemistry, "Calcium is one of the major ions in seawater. It is present in seawater at about 410 ppm the world over, so it comprises just under 1.2% by weight of the solids." That would put your suggested range of 400-420 spot on. Since an over abundance of calcium causes a reduction in alkalinity (and vice versa), it makes sense that alk levels never reached my target. What I'm having trouble wrapping my head around is why the imbalance of dosing (3:1) didn't drive down the calcium level. Oh well, I'll let calcium fall to the 410 range, and see how alk works out from there. Thanks for the heads up, BG!


That's the weird part... I've tested from 1 hour after dosing, to 24 hours after dosing, and it never goes above 7.3. It typically falls to 6.7 after 24 hours. I want my average to be 8.0, which means it'll have to be more than 8.0 initially, and below 8.0 before the next dose. I get that. What I'm not getting is my level ever going above 7.3. I can dose 50mL, or I can dose 100mL, and it's never more than 7.3. Yeah... it's like that.

What I'm finding (extremely) weird is that you're dosing more magnesium than anything else. I rarely dose mag, and my levels are always high. At best, I may dose 50ml mag per month. I'm using Kent TechM, as I picked up a few gallons at a great price. If you're using the powdered mix, it's possible that you may have mixed it at the wrong ratio. I'm beginning to wonder if I didn't do just that when I mixed my alk and calcium. We're only human... born to make mistakes.

I am sure I made the mag correctly. I am a chemist so that part is easy for me, plus I bought the pre-measured MgCl2/MgSO4 powder so no room for error, a monkey could do it. Just dump in the jug and fill to the top with RODI. I have never calculated the actual number of Mg ions/mL in the 2 part vs. the calcium in the 2 part. I did just add 1L of Mg yesterday to bring it up from 1200 t0 1300. I only added 100 mL of calcium and it was down to 410 and I dosed to bring it up to 450. That was the amount that the calculator said, as well as the max per day. I don't dose daily. I only test once a week and dose as needed. I don't have a ton of coral, and the ones I have are small frags. This tank has only been up and going since mid March so it is kind of empty looking in the coral department.
The good thing is I finally found a spot of coraline on one of my power heads. The only other place I have it is on a rock I bought to seed the tank that already had coraline. Nobody in my house could understand why I was so excited to find a spot of purple in my tank.
The tank seems to be doing really well. Fish are thriving and the corals are growing. Soon I can start raising the salinity in my QT tank to get my tangs ready to move over.

 

[snakeblitz33]

I'd try to get your parameters in line more with natural sea water. 410-425ppm calcium, 7.4-8dkh alkalinity.

At the end of the day, your tanks pH is the highest. When you add soda ash (sodium carbonate) at the end of the day, your pushing pH up, and it won't stabilize alkalinity. Using sodium bicarbonate slightly lowers pH because there is a little carbon dioxide that is offgassed. I'd use baking soda at night and soda ash in the morning. Bangs suggestion of blending the two will definitely work.

 

[lmforbis]

I was reading another forum and came across this article on the issue

http://reefkeeping.com/issues/2004-12/rhf/index.htm

 

[pegasus]

I was reading another forum and came across this article on the issue

http://reefkeeping.com/issues/2004-12/rhf/index.htm

Interesting read, but... I didn't find anything that would apply in my situation. I have "zero" nitrates, and I haven't done a water change in over two months. Even when dosing Alkalinity 3:1, my calcium is steadily going up, and alkalinity remains the same. My understanding is that sometimes you have to dose more of one and less of another to reach your target level. Once you get there, then a balanced addition of each should sustain those levels. I use RO/DI water for top-off, so there is no addition of calcium from that source. I have been adding an additional gallon of SW daily to raise my salinity, but even that water has balanced levels of alk/cal. I do run my mag at slightly elevated levels (1300-1400), but I don't think the small amount being consumed instead of calcium would account for the imbalance.

One thing I haven't tested is to see how high pH is after dosing alk. I've always tested in the late afternoon/evening, and it's currently 8.4. I'll try to test shortly after dosing alk to see how much of a spike there is. Not sure where the level is to destabilize alkalinity, but I'm not expecting it to spike too much. Time will tell...

 

[lmforbis]

The calcium carbonate does raise pH temporarily. Mine is typically 8.1-8.2.

 

[bang guy]

Pulling from what I've experienced, Carbonate Alkalinity stability depends on PH, Temperature, Calcium, Magnesium, Salinity, and Alkalinity levels. It's going to be difficult to get precise with that many variables. A PH of 8.4 and your high Calcium level is probably enough to put Alk in the edge though.

My plan 'B' is to introduce more Borate to your system. I didn't suggest as a primary plan because it adds complexity to testing your Alkalinity.

Try Plan 'A' first. I'm interested to hear what results you get.