alk dropping.. not sure why

[thisoldfish]

Hi all,

I'm running a 65 mixed reef with mostly SPS. I'm 2 part dosing and have had really consistent alk/calcium for past year. Because of some GHA I added GFO to get my phosphates to 0, which it is now. I did some routing testing a few days ago and found my dKh down from baseline 8.5 to 6! calcium was unchanged at 440. I calculated correction dose, got the alk back up and upped the dosing pump times to hopefully keep it stable. Today I found the dKh to be 7.6 and again upped the pump times.

My corals have been growing well- but fairly linear growth and I don't think there has been some recent expansion to explain the drop in alk.

Question: would the addition of GFO have anything to do with alkalinity? Am I just creating loads of iron carbonate?

Thanks

Brad

 

[ReefHomieJon]

When ph drops too low the alk will start to drop to bring the ph back up. Almost like a reserve for the ph. Maybe monitor your ph as well and try to keep that consistent. Just my $.02

as far as your question about GFO dropping alk, yea somebody answer that cuz I just added some Friday night and haven’t checked my water since so let us kno lol

 

[bdare]

When ph drops too low the alk will start to drop to bring the ph back up. Almost like a reserve for the ph. Maybe monitor your ph as well and try to keep that consistent. Just my $.02

as far as your question about GFO dropping alk, yea somebody answer that cuz I just added some Friday night and haven’t checked my water since so let us kno lol

This is totally false. pH dropping will not affect your Alk levels.

If you just started adding GFO, the drop in Alk is likely due to increased consumption by your corals. High phosphate can inhibit calcification of coral. If you drop phosphate then your Alk uptake probably increased.

 

[BeejReef]

What are you testing alkalinity with? Big, improbable swings are testing error, as often as not.
A popular digital alkalinity tester I use is prone to uncharacteristically low readings whenever I get to the bottom third of the bottle of reagents.

have you checked your dosing lines? re-calibrated your dosers? Dosing into high flow?
You say your levels were very stable for a year and you discovered this on "routine testing." How often is your routine? (no judgments). It's just that it may be important if this was a minor imbalance allowed become significant over many months, or a sudden swing.

 

[jlts21]

what is your mag level? Mag is essential in keeping cal & alk levels up. Due to me being lazy I never checked mag or dosed for it, but continued to have to dose alk. When I started checking mag and dosing accordingly, I stopped having to dose large amounts of alk

 

[ReefHomieJon]

This is totally false. pH dropping will not affect your Alk levels.

If you just started adding GFO, the drop in Alk is likely due to increased consumption by your corals. High phosphate can inhibit calcification of coral. If you drop phosphate then your Alk uptake probably increased.

6:00-13:45

 

[bdare]

Are you referring to the section where he talks about the rotting wrasse in your tank (10:00 mins in)?
All he's saying there is the rotting wrasse is going to cause the pH to drop because the rotting flesh is acidic. He's referring to a dkh "reservoir" which helps maintain a stable pH. It will not in fact DROP the alkalinity of your aquarium. That's a very confusing analogy he used there.

The alkalinity would not just vanish or melt. It's still suspended in your water column and would not be removed unless you physically removed it via a water change and replaced it with water at a lower DKH or it was consumed by some animal in the tank.

 

[ReefHomieJon]

Actually it was quite clear mr. totally false.
And yes, all “reservoirs” can be exhausted. That’s y it’s called a reservoir. At that point it’s not just suspended in your water column but gets released for your calcium CARBONATE skeletons of your stony corals back into your water column so until it levels itself back off which but if your dosing you won’t notice it or in his case he might be catching the fluctuation before it balances itself back out. At that point his corals will start to suffer. Antway, like I said, just my 2 cents. And the guy giving the speech. Don’t say it’s ABSOLUTELY FALSE unless it is.

 

[bdare]

Actually it was quite clear mr. totally false.
And yes, all “reservoirs” can be exhausted. That’s y it’s called a reservoir. At that point it’s not just suspended in your water column but gets released for your calcium CARBONATE skeletons of your stony corals back into your water column so until it levels itself back off which but if your dosing you won’t notice it or in his case he might be catching the fluctuation before it balances itself back out. At that point his corals will start to suffer. Antway, like I said, just my 2 cents. And the guy giving the speech. Don’t say it’s ABSOLUTELY FALSE unless it is.

Your comment insinuated that just because pH drops that Alk will drop. This is flat out not true. Sorry. Just don't want others getting the wrong idea.

 

[UCF Alum]

 

[Jeff Jarry reef]

GFO will make ALK drop but I don't know how much. I don't run my GFO wide open I let it trickle out slowly.

 

[bdare]

GFO will make ALK drop but I don't know how much. I don't run my GFO wide open I let it trickle out slowly.

I mentioned this above:

If you just started adding GFO, the drop in Alk is likely due to increased consumption by your corals. High phosphate can inhibit calcification of coral. If you drop phosphate then your Alk uptake probably increased.

 

[Jeff Jarry reef]

I mentioned this above:

If you just started adding GFO, the drop in Alk is likely due to increased consumption by your corals. High phosphate can inhibit calcification of coral. If you drop phosphate then your Alk uptake probably increased.

It seems like GFO does I guess because Everytime I put new GFO the ALK drops a little not much then levels out I a couple of days.

 

[thisoldfish]

ok- bunch to respond to here:

1- my "routine" testing is (usually) weekly.
2- I'd think it was the corals increased uptake but my calcium has stayed constant.. I'd think that would go down too if it was going to the corals
3- I'm using the Hanna-- and interesting what you say about the drop as the reagent gets low.. mine is low. But- I checked with my Red Sea alk and it's about the same, so I think it's legit low.
4- Mag is around 1275-1300, though I haven't checked in a few weeks. I hate checking Mag. I don't know why, I just do. I'll check it tonight.
5- yep, dosing into high flow and I've checked my lines. Haven't recalibrated the pumps.. didn't realize that was a thing. Maybe the pump is slowing down and delivering less dose... I'll have to measure. Good call.

Thanks all

 

[Dkeller_nc]

Its

Hi all,

I'm running a 65 mixed reef with mostly SPS. I'm 2 part dosing and have had really consistent alk/calcium for past year. Because of some GHA I added GFO to get my phosphates to 0, which it is now. I did some routing testing a few days ago and found my dKh down from baseline 8.5 to 6! calcium was unchanged at 440. I calculated correction dose, got the alk back up and upped the dosing pump times to hopefully keep it stable. Today I found the dKh to be 7.6 and again upped the pump times.

My corals have been growing well- but fairly linear growth and I don't think there has been some recent expansion to explain the drop in alk.

Question: would the addition of GFO have anything to do with alkalinity? Am I just creating loads of iron carbonate?

Thanks

Brad

It’s fairly typical for GFO to promote some degree of abiotic calcium carbonate precipitation. That’s one reason to use 0.1N HCl as the first step in GFO regeneration.

I’m rather surprised about the extent of the change you observed, however.

 

[BeejReef]

ok- bunch to respond to here:

1- my "routine" testing is (usually) weekly.
2- I'd think it was the corals increased uptake but my calcium has stayed constant.. I'd think that would go down too if it was going to the corals
3- I'm using the Hanna-- and interesting what you say about the drop as the reagent gets low.. mine is low. But- I checked with my Red Sea alk and it's about the same, so I think it's legit low.
4- Mag is around 1275-1300, though I haven't checked in a few weeks. I hate checking Mag. I don't know why, I just do. I'll check it tonight.
5- yep, dosing into high flow and I've checked my lines. Haven't recalibrated the pumps.. didn't realize that was a thing. Maybe the pump is slowing down and delivering less dose... I'll have to measure. Good call.

Thanks all

Hope u nail it down. RHF has written a number of articles on "apparent" excessive demand for alkalinity. If you search on here or even in google, it pops near the top. I don't know if that's what you're seeing. The basic logic is that the margin for error on calcium testing makes it easy to miss consumption and that it's best tracked over days/weeks.

My only other thought would be to test your saltwater storage bin. Occasionally, you hear about people getting a "bad batch," where one of the parameters is significantly out of whack. Obv., using that for WCs without corrective action will skew your parameters over time.

 

[Randy Holmes-Farley]

When ph drops too low the alk will start to drop to bring the ph back up. Almost like a reserve for the ph. Maybe monitor your ph as well and try to keep that consistent. Just my $.02

I don’t think that sentence makes chemical sense. I do not know of any mechanism in a Reef tank that makes lower pH cause alk to drop.

pH is determined mathematically by the alkalinity and the carbon dioxide level.

 

[Randy Holmes-Farley]

2- I'd think it was the corals increased uptake but my calcium has stayed constant.. I'd think that would go down too if it was

Yes it does, but to assume you will detect the expected calcium drop is the potential flaw in that reasoning.

You saw a 1.5 dKH drop in alk, and “no” drop in calcium. But the actual expected drop is only 10 ppm, a value that is smaller than the precision of most calcium kits. Thus it may have happened but wasn’t accurately observed with a hobby kit.

 

[Randy Holmes-Farley]

Your comment insinuated that just because pH drops that Alk will drop. This is flat out not true. Sorry. Just don't want others getting the wrong idea.

Agreed.