alk precipitation?

[Scott.h]

Chemically speaking, would a high level of one parameter cause precipitation of alkalinity?

85 gal total water volume. Because of a low demand tank and 10-15 gal weekly water changes I seldom dose alk. The new salt mix is slightly over 7. I've now eliminated the need for carbon dosing, and would like to raise slightly to 8-8.5 over the next weekish. Now the tank seems to suck it up without an apparent reason. Nothing else out of line. 1025, 440, 1350.. Also my ph could use a bump as its skirting around 7.8 day and night, but I'm assuming slightly raising alk should fix that.

I dosed almost 3 teaspoons of ash/RO spread over 5 dosings in the last 24 hours (checking dkh before each dosing). Still 7kh, ph 7.8. Precipitation, test error, or keep dosing? The obvious thing is to keep dosing, but my question- chemically speaking is some of alkalinity apt to precipitate as I try to increase?

 

[redfishbluefish]

Something is not right. A low demand tank that has been dosed with 3 tsp of Soda Ash should boost dKH by 2.3. And I can't see you "consuming" 2.3 dKH in a low demand tank....actually any tank. Also, assuming your test numbers are correct, you will not get carbonate ppt at those levels. I'd go back and take a look at your testing....maybe have a friend or LFS verify your numbers.

 

[Scott.h]

I agree. however if my alkalinity isnt accurate my pH should also be elevated. tested both parameters twice yesterday and once this morning.

 

[Scott.h]

I misspoke. I'm using a 1/2 teaspoon measuring spoon so I dosed 1.5, not 3

 

[Randy Holmes-Farley]

I agree. however if my alkalinity isnt accurate my pH should also be elevated. tested both parameters twice yesterday and once this morning.

pH is controlled by both the CO2 level in the water and the alk. So pH is not a good guide to the alkalinity unless you know the CO2 level.

It could just be a combination of demand and inaccuracy in the testing.

In any case, 7 dKH is fine.

 

[Luke Schnabel]

What test kits are you using. When I raise my Alk up I typically to right when lights go off to offset the PH spike. If your using soda ask your PH will rise but you need to understand the realitivly of PH and CO2 in the air

 

[Scott.h]

pH is controlled by both the CO2 level in the water and the alk. So pH is not a good guide to the alkalinity unless you know the CO2 level.

It could just be a combination of demand and inaccuracy in the testing.

In any case, 7 dKH is fine.

On that note my refugium has a 10' drop to the basement. I do my dosing into my skimmer basket. Is it possible after it drops, runs through the skimmer, drops through all the channels, and pumps back to the display, the co2 might have a minimal impact affecting ph anyway? At a slow stream?

Over the last 48 hours kh has raised from 7 to 7.5. It just took more ash then I thought it should. I'll retest tonight. But won't keeping alk at 7 flat stunt the sps growth more so then if it were 8? Or does that not matter?

 

[Scott.h]

What test kits are you using. When I raise my Alk up I typically to right when lights go off to offset the PH spike. If your using soda ask your PH will rise but you need to understand the realitivly of PH and CO2 in the air

I like using the API test for kh. Hanna has had a lot of issues with the digital. Typically I don't like API but I feel there is enough of a gradual difference in color change, even if not accurate, I can keep that level stable. And you're right, I do my testing right at lights dimming during the same time typically. My ph has been low, but pretty darn stable no matter when I test as of recent.

 

[Luke Schnabel]

If it's stable at 7.8 I wouldn't worry much. But if you can stable it at 8-8.2 that would be better...

 

[Scott.h]

If it's stable at 7.8 I wouldn't worry much. But if you can stable it at 8-8.2 that would be better...

i agree. It's odd. It used to run 8.2 during the day and 8.1 overnight. My alk is running slightly lower now (.5). My new water 24 hours mixed reads 8.2, so I'm not sure what's going on. Since the weather changed I even left all the windows open, and turned off the pilot to the fireplace just to see if it had an impact. It didn't. I know 7.8 is ok, but figured my sps would be better suited with a bump of alk and ph. Maybe I'm just being OCD.

 

[Randy Holmes-Farley]

On that note my refugium has a 10' drop to the basement. I do my dosing into my skimmer basket. Is it possible after it drops, runs through the skimmer, drops through all the channels, and pumps back to the display, the co2 might have a minimal impact affecting ph anyway? At a slow stream?

Over the last 48 hours kh has raised from 7 to 7.5. It just took more ash then I thought it should. I'll retest tonight. But won't keeping alk at 7 flat stunt the sps growth more so then if it were 8? Or does that not matter?

pH is determined mathematically by alkalinity and CO2. So there is no uncertainty about the effect, only the amount of CO2 in the water. Good aeration will drive the CO2 level toward equilibrium with the level in your home air, which may be like outside air, or a lot higher in CO2 (yielding lower pH).

 

[Scott.h]

pH is determined mathematically by alkalinity and CO2. So there is no uncertainty about the effect, only the amount of CO2 in the water. Good aeration will drive the CO2 level toward equilibrium with the level in your home air, which may be like outside air, or a lot higher in CO2 (yielding lower pH).

Ok, out of curiosity, assuming the co2 inside the tank water is equal to the co2 outside the house, is there a way to lower co2 therefore raising ph? Ph buffer? But if I remember correctly you suggest stay away from buffers correct?

 

[Scott.h]

Also I tested kh again. Right back to 7 flat. Which makes me think it's precipitating. How could it stay consistent 7 just from a 17% weekly water change without dosing, then for two days I add a considerable amount of ash raising it, only to have it be right back at 7 twenty four hours later? If the tank is using it, ok, but if it were, I would have had to raise it before as well, right? To keep it at 7 previously..

I understand it's within spec but I'm trying to understand what's going on chemically to make these things happen. I appreciate the feedback

 

[Waterjockey]

Ok, out of curiosity, assuming the co2 inside the tank water is equal to the co2 outside the house, is there a way to lower co2 therefore raising ph? Ph buffer? But if I remember correctly you suggest stay away from buffers correct?

Some people build co2 scrubbers and put them on the air intake to thier skimmers. Basically a pop bottle or similar filled with soda lime, a few holes drilled in it, and attach airhose from skimmer. I'm sure there is a thread on reef2reef somewhere on CO2 scrubbers if you want to do a quick search

Cheers!

 

[HanKami]

Had the same problem, these step work for me, if you running gfo turn it off, I believe that was killing my alk. After removing it I did a water change, I have 150g system I did a 30g water change. Next I used a bulk reef supplies reef calculator to see how much a&b to dose to keep my levels where I wanted them. I also ran my skimmer air intake line out my window for fresh air( my preference) after 1 week I was spot on.

 

[Scott.h]

Had the same problem, these step work for me, if you running gfo turn it off, I believe that was killing my alk. After removing it I did a water change, I have 150g system I did a 30g water change. Next I used a bulk reef supplies reef calculator to see how much a&b to dose to keep my levels where I wanted them. I also ran my skimmer air intake line out my window for fresh air( my preference) after 1 week I was spot on.

Wow that's interesting. I recently changed from Phosguard to BRS media, using their suggested amount. I wonder if the brown iron based gfo is why I'm seeing the change..

 

[Randy Holmes-Farley]

Ok, out of curiosity, assuming the co2 inside the tank water is equal to the co2 outside the house, is there a way to lower co2 therefore raising ph? Ph buffer? But if I remember correctly you suggest stay away from buffers correct?

Sure, we discuss it several times ever day.

No, buffers are not the way.

You can bring in outside air, either by windows, air exchanger, or airline to skimmer inlet.

You can use a CO2 scrubber on a skimmer inlet.

You can use limewater (kalkwasser) or a grow more organisms that use CO2 (macroalgae, corals, etc.).

This has more:

pH and the reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/

 

[Randy Holmes-Farley]

Had the same problem, these step work for me, if you running gfo turn it off, I believe that was killing my alk. After removing it I did a water change, I have 150g system I did a 30g water change. Next I used a bulk reef supplies reef calculator to see how much a&b to dose to keep my levels where I wanted them. I also ran my skimmer air intake line out my window for fresh air( my preference) after 1 week I was spot on.

The iron in GFO accelerates precipitation of calcium carbonate, which is why it can clump and even show precipitation downstream of it.

Reduced phosphate can also accelerate coral growth, which consumes more calcium carbonate and may allow abiotic precipitation of calcium carbonate to proceed faster.

Reduced organics, which GFO can also contribute to, will also potentially accelerate abiotic precipitation of calcium carbonate.

 

[Scott.h]

There is something definitely going on chemically. I've dosed 3 different times getting my levels from 7 to 8. 24 hours later it's right back to 7. If I don't dose swat it stays at 7. And my calcium tests a solid 440 all through the week. Makes no sense. I'm about ready to go full apex with 2 dos dosing pumps and call it a day.

 

[Randy Holmes-Farley]

There is something definitely going on chemically. I've dosed 3 different times getting my levels from 7 to 8. 24 hours later it's right back to 7. If I don't dose swat it stays at 7. And my calcium tests a solid 440 all through the week. Makes no sense. I'm about ready to go full apex with 2 dos dosing pumps and call it a day.

I'm not sure it isn't making sense. The calcium drop associated with a 1 dKH drop in alkalinity is only about 6-7 ppm, which you probably couldn't see with a kit.

Stick to equal parts dosing based on the alk need UNLESS calcium is already too high or too low and you'll be fine.