My calcium and alkalinity demand are out of control and I’m not sure what’s happening

Brett S

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I have a 220G tank with maybe a medium low to medium SPS load. Back in December I was dosing about 100ml of BRS calcium and alkalinity a day to keep my calcium at about 460 and my alkalinity at about 8.6. I use the trident for my calcium and alkalinity testing and a DOS for dosing. I use the trident controlled dosing, so my daily dose goes up and down a little, but it was averaging around 100ml a day. My pH would range daily from about 7.95 to about 8.1.

At that time I started playing around a bit with dosing lye for alkalinity and also using a CO2 scrubber to raise and stabilize my pH. Over time I raised my pH to a daily range of about 8.15 to 8.3 and naturally this increased my calcium and alkalinity demand, but I feel like it has increased it well beyond what it should have. I’m now dosing about 600ml of calcium and alkalinity a day with very little increase in the coral load. I can’t imagine that a slight increase in pH would increase my calcium and alkalinity demand 6 fold, but I’m not really sure what’s happening or where it’s all going.

Other than a little cloudy water right where the alkalinity drips in, which dissipates immediately, I’m not getting any precipitation when the calcium or alkalinity is added. However, if I don’t scrape the tank glass I get a white calcium build up on the inside of the tank glass within a week or two. My return pumps will also stop running with an overcurrent warning about every 2 or 3 weeks. When I disassemble them to clean them I find the impellers nearly seized with calcium buildup. I use acid to remove it, but a few weeks later it’s back and the pumps stop again.

If I try scaling back a bit on my calcium and alkalinity dosing the calcium and alkalinity levels in the tank drop, so I think that indicates that something is using it and that it’s not just precipitating out somewhere, but I’m kind of at a loss as to what to do. I’m dosing both soda ash and lye, using the apex to pick one of the other, based on the current pH level. The apex also controls the use of the CO2 scrubber based on the pH level, so I tried adjusting the programming to drop the pH level down a bit, so now it’s ranging between about 8.05 and 8.2, but I’m still using 600ml of calcium and alkalinity a day.

I calibrate the trident every time I change the reagent and it’s never been off by much when it gets calibrated, so I don’t think that my calcium and alkalinity are too far off from 460 and 8.6dKh, but I did order salifert test kits for calcium, alkalinity, and pH just to make sure that the levels really are where I think they are. Those should be coming in the next few days.

Any other thoughts on what might be going on here or what I can do to get things back to normal in the mean time?
 
Lazy's Coral House

rtparty

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You've got major precipitation going on. The pumps tell you this. If it's not building in a sand bed, your pipes are likely being coated with precipitation.

I'd start with a few large water changes. Try to get things back to normal. Send off an ATI ICP test as well. I bet your chemistry is all out of whack.

Also, turn off the Trident controlled dosing before things get worse. Just increase it yourself with numbers that make sense
 
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I'm no expert by any means. Would kalkwasser maybe be a better route?

I recently learned that kalkwasser isn't good for big calcium increases.

I think it was for every 20ppm increase in calcium, Kalk will give you an ALK increase of 2.8 ppm.

So if you want to increase your calcium using Kalk 60 ppm, you will increase your ALK by 8.4 dKH.
 
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Brett S

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You've got major precipitation going on. The pumps tell you this. If it's not building in a sand bed, your pipes are likely being coated with precipitation.

I just checked the sand and it still seems to be loose and sandy, so I don’t think there’s precipitation going on there. I don’t think it’s happening inside the pipes either. Other than the impeller, the rest of the inside of the pump was perfectly fine.

Also, turn off the Trident controlled dosing before things get worse. Just increase it yourself with numbers that make sense

I don’t think the trident controlled dosing will make anything worse. It still operates within certain limits. It’s not like the trident controlled dosing jumped from 100ml to 600ml. I had increased the limits over time as my alkalinity and calcium demands went up.
 
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Brett S

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It seems to me that ordering the other test kits to confirm the trident results sounds like a great idea. It seems incredibly unlikely that your alk consumption quickly went up 6 times.
Do you remember if the dosage changed after a reagent replacement?

Yeah, given that I calibrate the trident regularly I would be pretty surprised if those readings were off, but I’ve been surprised before. I think it definitely makes sense to get some additional verification.

The dosage has gone up over time as I’ve noticed that the calcium and alkalinity levels were dropping. The trident controlled dosing uses a base level and is set to only increase the dose by 35% of that base level, so as I noticed that my alkalinity and calcium were dropping even when the system was dosing at 35% over the base level I would increase the base level. It would stabilize for a while, but after a few weeks the levels would start dropping again, so I would increase the base level again, until we got to this point. This all happened slowly over the last 8 or 9 months.

Each time the reagent was changed I calibrated the trident and didn’t see any significant changes to the dosing or calcium/alkalinity readings.
 
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Brett S

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So one more thing to add. I just noticed tonight that my salinity has managed to creep all the way up to 41ppt. It usually stays pretty stable around 35ppt, so I don’t check it very frequently. Obviously I should check it more often than I do. I’m not sure if this is a result of the huge additions of calcium and alkalinity, or if this is causing the high calcium and alkalinity demand or the precipitation on my pumps, or if this is just completely unrelated.
 

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Yeah, given that I calibrate the trident regularly I would be pretty surprised if those readings were off, but I’ve been surprised before. I think it definitely makes sense to get some additional verification.

The dosage has gone up over time as I’ve noticed that the calcium and alkalinity levels were dropping. The trident controlled dosing uses a base level and is set to only increase the dose by 35% of that base level, so as I noticed that my alkalinity and calcium were dropping even when the system was dosing at 35% over the base level I would increase the base level. It would stabilize for a while, but after a few weeks the levels would start dropping again, so I would increase the base level again, until we got to this point. This all happened slowly over the last 8 or 9 months.

Each time the reagent was changed I calibrated the trident and didn’t see any significant changes to the dosing or calcium/alkalinity readings.
I recently did a reagent swap and recalibrated my trident and my calcium reading dropped by 100, so I love my trident but I think from here on I will be calibrating it with my tank water. I don't trust the calibration solution.
However, I though you were talking about a quick change. If this happened over 9 months then I'd say it likely may be correct but still a good idea to verify your parameters.

Raising salinity is a side effect of 2 part dosing. Most people don't dose enough to really see the effect but at 600ml a day I'm not surprised you saw a salinity increase
 
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A couple of thoughts:
1. Increased pH increases biological and abiotic consumption. However, 6 fold seems like too much. In my tank I recently dropped my pH by about 0.05 and my alk consumption dropped from 1.2 to about 0.8 or a 25% drop.
2. It looks like you are dosing a 2-part which will definitely increase your salinity over time. Hence, many people add a 3rd part to account for this.
3. Check your sand under frag plus and rocks for clumping.
 
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Brett S

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So just a quick update on this. My Salifert calcium test kit came today and that read 450ppm while the trident is reading 474ppm. They are close enough that I believe that my calcium is in a good place.

Unfortunately it looks like my alkalinity and ph test kits won’t get here until later this week, but as soon as they arrive I’ll let you know what I find.

In my box of random fish supples I did find some old API pH test strips. They expired in 2016 and I’m not sure that test strips are the most accurate to begin with, but I did use one just to see what it would come up with and it puts my pH right at 8.5. My apex is reading 8.2, so if the test strip is to be believed, then it’s possible that my pH is a bit higher than I thought it was. However, I’m not sure how much faith I can put in test strips that expired 5 years ago. Before I make any adjustments I’ll wait until the Salifert pH test kit arrives.

Also, I did check my sand and it seems loose and sandy with no clumping, so I guess that’s a good sign.
 
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Brett S

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My Alkalinity and pH test kits showed up today. Alkalinity was not a surprise… Salifert and Trident were within .2dKH. However, it looks like my pH is a good bit higher than I thought it was. Right now my apex is reading a pH of 8.15, but the salifert test kit puts it at more like 8.5,

8.5 is definitely on the high side, but it’s not like crazy high. I’m not sure if that’s really enough to cause calcium build up in my pumps and cause this really high calcium and alkalinity demand. What do you guys think?
 

guylaga

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If your tank is going over a pH of 8.4 that could be causing excessive abiotic precipitation on your pumps / equipment.

Would it be possible to drop your PH by .1 or .2? I would try that and monitor to see if this helps with the precipitation.
 
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Brett S

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If your tank is going over a pH of 8.4 that could be causing excessive abiotic precipitation on your pumps / equipment.

Would it be possible to drop your PH by .1 or .2? I would try that and monitor to see if this helps with the precipitation.

Yeah, I plan to do that. My pH naturally tends to run very low, so I’ve been working to get more control over pH by allowing the apex to switch between lye and soda ash for alkalinity and also turning on or off a CO2 scrubber. I’ll dial down the pH target by .1 for now and then in a couple of days I’ll decrease it by another .1.

I think I’m also going to get another pH probe. The one I’m using now is the one that came with my apex, which would make it more than 4 years old. I have recalibrated it several times in those 4 years, but the last calibration was probably a good 8 or 10 months ago.

Thanks for the reply:)
 
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Brett S

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Well, after a frustrating few days I finally figured out why my salinity level was rising. I have a DOS that does an auto water change, changing about 3 gallons per day. In an attempt to lower the salinity I adjusted the ratios a bit so it was pulling out more water than it was putting back in. That way the ATO would make up the rest with fresh water and the salinity should go down over time.

But I kept making bigger and bigger adjustments and my salinity still kept rising. It finally got to the point where I was pulling out water, but I wasn’t adding any new salt water at all and the salinity still wasn’t going down.

After hitting my head against the wall for a bit, trying to figure out how that was even possible I finally discovered that the waste water line for my water change DOS had gotten clogged, so even though the DOS was running it wasn’t actually pulling out any water. So, apparently for some period of time the water change had been adding salt water, but not removing any old water and that’s what caused my salinity to go up.
 

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