"When" does Alk precipitate?

[Brian Lenny]

I'm dosing a huge amount of Alk and Calc (600ml / day) into my 280G tank. I'm pretty sure it's precipitating out or getting absorbed. I don't see obvious signs of precipitate, but much of my plumbing runs under the floor, so it could be anywhere.

My question is WHEN does Alk precipitate? If I add a tablespoon of Alk, I see my level go up by 0.5 dKh or so. Does this mean that the water has "taken in" this amount of Alk and it didn't precipitate out? Or, can it precipitate out over time?

I keep my Mag above 1400 and always add the same amount of Alk and Calc. My pH goes between 8.0 and 8.2 -- at lower pH levels, is it possible that the Alk might precipitate out? I'm pretty much giving up. Hope to change salt to Red Sea Coral Pro that mixes higher.

Thanks!

 

[Randy Holmes-Farley Verified Community Expert]

Precipitation does not need to happen instantly, and most often will not. It is a steady, ongoing process where fresh surfaces of calcium carbonate attract more to precipitate on top of it.

The process is speeded by high alk, pH, temperature, and calcium, and reduced by high organics, phosphate, and magnesium.

 

[Randy Holmes-Farley Verified Community Expert]

How much alk in dKH per day does that 600 mL correspond to? It may not be excessive.

 

[Brian Lenny]

How much alk in dKH per day does that 600 mL correspond to? It may not be excessive.

Using Bulk Reef Supply additives, 600ml per day equals 3dKh. I have ~10 LPS corals (around the size of a softball or larger) and ~5 leather corals (also softball sized or larger). Coraline is slowly taking hold (very slowly). The tank is 7 months old. I dose my Alk and Cal in 45min spurts (100ml each) and alternate between Alk and Calc with 30min rest period in between.

I'm using Kent Reef Salt at the moment and will start to change to Red Sea Coral Pro (to get to ~10dKh, which is my target) -- and I'm curious as to why water with one salt mix (Kent) won't "hold" Alk at a higher level, whereas Red Sea comes preset to mix at a certain level. Wouldn't the ability to hold Alk be similar (given the RODI is the same)?

Finally, how important is it to get to a higher pH? Can I get to 10dKh with 8.0-8.2 pH? I heard a recent MACNA talk indicating a link between these two and possible destabilization of Alk at lower (8.0) pH.

Thanks!

 

[Bubbythebull]

Precipitation does not need to happen instantly, and most often will not. It is a steady, ongoing process where fresh surfaces of calcium carbonate attract more to precipitate on top of it.

The process is speeded by high alk, pH, temperature, and calcium, and reduced by high organics, phosphate, and magnesium.

I totally agree, I have a system that I don't dos and only do weekly minimal water changes to the tank is covered with precipitation.I think the main reason is because I am very consistent with the levels in this tank. I have another reef system that I dose and keep the alk at a higher level...but don't do w/C's that consistently... And notice there isn't much precipitation

 

[BeejReef]

Using Bulk Reef Supply additives, 600ml per day equals 3dKh. I have ~10 LPS corals (around the size of a softball or larger) and ~5 leather corals (also softball sized or larger). Coraline is slowly taking hold (very slowly). The tank is 7 months old. I dose my Alk and Cal in 45min spurts (100ml each) and alternate between Alk and Calc with 30min rest period in between.

I'm using Kent Reef Salt at the moment and will start to change to Red Sea Coral Pro (to get to ~10dKh, which is my target) -- and I'm curious as to why water with one salt mix (Kent) won't "hold" Alk at a higher level, whereas Red Sea comes preset to mix at a certain level. Wouldn't the ability to hold Alk be similar (given the RODI is the same)?

Finally, how important is it to get to a higher pH? Can I get to 10dKh with 8.0-8.2 pH? I heard a recent MACNA talk indicating a link between these two and possible destabilization of Alk at lower (8.0) pH.

Thanks!

I'm not an expert at all, but if you watch the BRS salt video series, you'll see that the "highly enriched" salts, notably the one you're thinking of switching to, actually do lose a goodly chunk of their advertised alkalinity and calcium content within a day of mixing.

They kind of wiggle around it by saying that these salts are designed to not be mixed that long and used immediately.
Personally, I fail to see what the difference would be, being mixed in a salt storage barrel or being further mixed by a return pump and powerheads. To my mind, in either scenario, it would be likely to precipitate... though I'm always willing to stand corrected.