Can't raise alkalinity

[jccaclimber]

I've always puzzled about threads asking this, but now I find myself in this situation. All testing values are via Trident, and I have not changed the reagents during this time. Dosing is normally via dosing pumps into a high flow area of the sump.
A couple weeks ago my Alk was ~11 Ca 450, Mg 1400. Added a CO2 reactor to pull the pH up and watched it slowly decline (with slightly increasing dosing) to Alk 9, Ca 420, Mg 1390. I ran out of Mg supplement and had the skimmer run wet for a day and haven't corrected it, so the Mg is currently claiming 1330. Alk 8.5, Ca 381. Daily pH swing is 8.0->8.25. I'd rather be at 9.5 Alk/450 Ca.

Upping the 2 part dose hasn't really done anything, so I tried manually dosing Alk (liquid soda ash). This has resulted in my Ca decreasing (381), but the alk isn't increasing.
6:10 PM: 8.54 dKh.
8:15 PM: I added liquid to raise it by ~0.7 dKh
8:50 PM: 8.82
12:20 AM: 8.61
6:10 AM: 8.55

I don't think my pH is high enough to warrant precipitation, I'm not seeing any on the heaters/pumps/glass and the water is not cloudy. That said, I can't imagine it's being consumed that fast either. I have had greatly increased coraline growth the past month since putting the CO2 reactor on, but I don't think that explains pulling it down as fast as I see after dosing (and not the rest of the time). Ideas?

 

[Coral Me Impressed]

With out seeing the tank and knowing the rest of the test results like No3 and Po4, how mature and stocked the tank is. But without that if your coral look happy it's probably just from growth. It's not uncommon for a mature tank to use up more then 1 dkh per day. When I had a similar experience I found out that my dosing pump failed. The coraline will also soak up the elements.

 

[jccaclimber]

It isn't the total daily consumption that has me confused, it's the fact that I can't put in a manual adjustment.
My current dosing rate has been keeping alk stable at 8.4 to 8.6 this week, measured every 6 hours. If I do nothing other than the scheduled dosing it'll be the same at this time tomorrow. The only time it seems to vanish is if I try to raise it, in which case it's right back where I started several hours later.
I understand that consumption increases with increased alk, but the relationship isn't that steep.

NO3 is 0-5 depending on how recently I've dosed it. Been up a bit under a year. Feeding a sheet of nori and cube of mysis most days. Few couple year old tangs and a mixed reef. Fish and coral, but not rock, moved from a prior tank due to a move. Most of the coral is doing ok, but not quite how I'd like for the current maturity level of the system, although my main question is why I can't move the alk around, not why X coral is or is not doing well.

 

[Coral Me Impressed]

Ah, I didn't catch that. Have you tried a manual test to confirm what the trident is showing. It might be because I've been screwed in the past but personally I wouldn't trust any change without confirming it with another test.

 

[jccaclimber]

Ah, I didn't catch that. Have you tried a manual test to confirm what the trident is showing. It might be because I've been screwed in the past but personally I wouldn't trust any change without confirming it with another test.

I've checked it with an API kit which is starting to turn at 8, and clearly turned by 9, so it passes the sanity check.

 

[Fugepower]

If I read right you said you ran out of magnesium are you still out? Also of your mag is to low you wont buffer right but I'm sure you already knew that. Sorry if I misunderstood I'm just trying to offer my insight

 

[King Turkey]

perhaps a water change then try?.

 

[tores]

It sounds like it is precipitating. I had that issue. Changed my dosing to do small amounts throughout the day (24 doses). I now maintain alk with less than half the dosing (soda ash) as compared to before...

 

[jccaclimber]

If I read right you said you ran out of magnesium are you still out? Also of your mag is to low you wont buffer right but I'm sure you already knew that. Sorry if I misunderstood I'm just trying to offer my insight

Yes. Still out. I should have more next week. I agree that low Mg is hurting me, but it doesn’t seem like it’s low enough to push my Alk that low.

perhaps a water change then try?.

Maybe, but I hate not knowing why something works.

It sounds like it is precipitating. I had that issue. Changed my dosing to do small amounts throughout the day (24 doses). I now maintain alk with less than half the dosing (soda ash) as compared to before...

Most of my dosing goes in during many steps through the day. I recently changed my dosing from 120 mL/day to 150 with no noted change. I could push more to see what happens, but not that long ago it was at 90 mL/day and doing fine (albeit a low consumption rate).

 

[tores]

You might need to dose it in a higher flow area somehow. The alk is obviously going somewhere. Mine paired up with Ca around the heater - I discovered a nice thick layer. White dots on the glass too. Next up is cleaning the pump... BRS TV recently had a few good episodes on 2-part and precipitation. They recommended putting a powerhead in the sump for higher flow. I seem to manage without right now. I guess you could try hand-dosing into the tank at a powerhead to get the levels up and then run with lower dosing in the sump... From what I recall, the type of 2 part matters. Bicarbonate is less prone to precipitation. I use Soda Ash.

I used to dose 55ml in my 65 gal - I am now at 21ml/day.

 

[jccaclimber]

My manual adjustments were added in front of the return outlet in the display.
Trying a different Alk source would be easy to do.

 

[King Turkey]

I best guess would be somthing is not balanced. But hard to say. That was the only reson i suggested WC as a sorta balance till till you figure it out. Sorry I was not much help.

 

[jccaclimber]

I don't know why, but I'm leaning toward precipitation. I noticed my alk at 8.3 this morning. I opted to try dosing then since it's at the low point in pH, and it seemed to hold. It's at 8.9 dKh now, will see what it does tomorrow. My pH isn't nearly as high as it has been in the past, so I'm not sure why I'd be having a precipitation issue now and not then. I'm also not sure where it's going as I'm not seeing signs of it that I've seen in the past.

 

[King Turkey]

@Randy Holmes-Farley insight?

 

[Randy Holmes-Farley Verified Community Expert]

I can't really tell how much alk you are adding and with what product. perhaps you are not adding as much as you think. Lots of people make that mistake due to using an incorrect calculator, wrong solution, dosing pumps off, etc.

precipitation happens in all reef tanks, and goes faster as pH and alk rise.

Finally, I'd add that an alk of 7-8 dKH is perfectly fine and trying to keep it higher may be more trouble than it is worth.

 

[maroma]

Hello Reefeers,

Need help I can't raise my DKH stay 5.3 to 6.2 back down one thing I removed was Kalk yesterday
Notice my 60/gallon white I thought it shot up the PH but it read about 7.4 that was weird any suggestions.

 

[Randy Holmes-Farley Verified Community Expert]

Hello Reefeers,

Need help I can't raise my DKH stay 5.3 to 6.2 back down one thing I removed was Kalk yesterday
Notice my 60/gallon white I thought it shot up the PH but it read about 7.4 that was weird any suggestions.

I cannot understand what you are saying, but your pH is not 7.4.

if you add 2 dKH with baking soda over a couple of days, what happens?

 

[maroma]

LOL!!!!

This is what happens when you do this driving.

All good - found why my alkalinity was not rising pass 6.3.

Thanks

 

[jccaclimber]

Long term follow up on this.
Using soda ash and CaCl from BRS, typically dissolved in RODI per the instructions.
It didn't seem to matter if I put in 100 mL/day, or several times that.
When I moved the tank a couple months later I did find a lot of sand (it's a bare bottom tank) in the sump and corners of the tank. I suspect a lot of this was precipitation. I also found a fair amount of precipitation on the outside (not inside) of my COR20 return pump. Ultimately I feel that the volume of 2 part added far exceeds the amount of precipitation I found, but that's a separate issue, and I do believe precipitation was the cause.