Sandbed precipitation

[drtechno]

Hi all

I've been studying the forums about precipitation, dosing, new tanks, etc. And sure enough, with a 6 month old tank, I have been dumping tons of alk and ca into the system without significant changes. So after all the reading on the forum, I realized I am precipitating as the sandbed is hard. No precip on the equipment tho, but the sandbed is pretty definitive.

System info - 200g tank + 50 gal sump, dosing 2 part (BRS soda ash) as well as Kalk. Running CO2 scrubber.
pH 8.0-8.2
Alk 7.2
Ca 400
Mg 1440
Nitrates unfortunately I think are 0 despite some algae growth and dumping food in the tank liberally.

The tank is only stocked with a dozen or so new frags, half LPS, half easy acros (green slimer, etc). So basically not stocked at all

I don't think the exact doses of 2 part and Kalk matter at this stage because my questions are more general. I have seen the advice given to other reefers and would like further explanation.
The advice Randy has given - back off pH, stop dosing for a while then eventually start up again slowly.

So - I know that my dKh will drop below 7, as it dropped to 6.5 just when I reduced my kalkwasser by 50% to 1 gal/day. I am wondering if the dkh may even go to 5.
First questions are about the coral frags already in the system--
*Is there a floor dKh at which I should restart some 2 part dosing in order not to lose the acro frags?
*Will dropping the dKh below 6 for a small period of time severely impact the small frags I already have?
I assume I need to back off the dosing slowly so as not to make dramatic changes for the corals

Second set of questions are about the goals of reduction - I know it is to interrupt the precipitation event - but how do I know when that has occured ? How do I know when I have backed off enough?
*Do I reduce my pH and alk and keep it reduced until the sandbed starts to soften ?
Or, do I simply reduce the pH and alk "for a couple days" and then restart dosing slowly - regardless of whether the sandbed is softened up or not?
*Will the sandbed break up/soften over time?

Is this entire thing just to break the cycle of the precipitation event (which is a finite thing), and then start up dosing again? Or is it a long term reduction until the sand grains are coated with whatever things are in the tank (phosphates, bacteria, etc).

Thanks for any advice you all can give.

BTW - if Randy ends up reading this - I was floored that I live like 2 towns away from you, LOL. Crazy that we have such a talent so local!

 

[Miami Reef]

Here’s a general guide to preventing precipitation:

Keep phosphates, magnesium, and organics on the moderate to high side.

Use sodium bicarbonate as your alkalinity additive, as it has a very slight pH lowering effect, which is desirable in this case.

Keep alkalinity on the lower range.

Fresh calcium carbonate will add as a seed crystal to further precipitate more calcium carbonate. The goal is for the organics and phosphate to coat these fresh surfaces to stop the feedback loop. After a while, you can slowly restart with the pH-boosting additives.

About the sand clumping, I’m not sure if it will unclump with time. It will be a question for someone else to answer.

You are so lucky to live near Randy. I wish I can meet him one day. He’s my hero.

 

[BigMonkeyBrain]

Your reported tank parameters should not cause a precipitation event. You do say you dose Kalkwasser - what does the PH rise to during / after the dose ?

If you let your PH decline it may soften the newly formed CC in the sand bed. If you let your Alk decline ( 6.0 dkH) I do not think it will dissolve CC nor do I think it will hurt your corals in the short term. I would suggest keeping your Alk up (7.0 dkH) by another additive that does not raise your PH so strongly - like baking soda - or a mix with soda ash and see it the precipitation is caused by the Kalkwasser.

From what I've read - Randy and others - precipitation happens constantly in the super saturated sea water - some CC forms and some CC dissolves and during larger event it is interrupted by Magnesium or until the water is depleted of Alk ( carbonate / bicarbonate ).


Probably happens !

 

[drtechno]

Thanks. I was using soda ash as I want to boost my pH to 8.3, and I am still 8.1 ish. So I do/did want a pH-boosting additive (eventually?). I am already using a co2 scrubber, and have a dedicated air exchanger just for the fish room, so the 'fresh air' and less co2 route is already maxed. But I will let the pH fall back down as I stop the kalk and 2 part dosing. I may keep the scrubber running just to keep the pH ~7.9.

When do I know when I can restart dosing? Are we talking days or months? If I am waiting for organics to coat the surfaces, I feel like that is a months long process with heavy feeding.

 

[drtechno]

Your reported tank parameters should not cause a precipitation event. You do say you dose Kalkwasser - what does the PH rise to during / after the dose ?

Hah.. Ok, I will sheepishly disclose my dosing - I was dosing 2 gals of kalk and 160cc ea 2part (per day) in an effort to get my Alk up with the pH I had. That's a ton (from what I understand) given that there is no alk usage in the tank

Before I went on this pH raising expedition, I was able to get my alk and ca to wherever I wanted with 2 part (9 dkh and 425 ca) but wanted my pH to move higher.. so I started dumping more soda ash (unbalanced) to the tank. I think I was at 125 cc alk and 25 cc of ca in pursuit of that effort. Since soda ash wasn't working, I started dumping kalk. And the whole thing started up there. Where my problems began.

 

[Miami Reef]

When do I know when I can restart dosing? Are we talking days or months? If I am waiting for organics to coat the surfaces, I feel like that is a months long process with heavy feeding.

Good question.

I personally don’t have any data, but I’d assume within a week or two you can slowly start back up again. However, I would caution to take it nice and slow to prevent it from happening again.

 

[Randy Holmes-Farley]

Second set of questions are about the goals of reduction - I know it is to interrupt the precipitation event - but how do I know when that has occured ? How do I know when I have backed off enough?

Only time can tell, and the time is based on empirical results with others. There's no way to directly observe it. it takes time for the surfaces to become "poisoned" with things that interfere with precipitation (phosphate, magnesium, organics, bacteria, etc.) how fast that happens depends on how much of those are in the water, but a few days is usually enough. It never hurt to wait longer.

Corals are fine at 6 dKH.

 

[drtechno]

One other question I have been struggling with, is even if I go slowly in raising ph and alk after I break the cycle, am
I destined to end up with precip again? ie- will repeating the same dosing regimen with the same pH elevation result in the same outcome? I guess the answer will be it depends on the amount of surface poisoning.
Or should my goal be lower alk and pH until I get more coral load into the tank, at which point I can start going up on dosing again?

 

[Miami Reef]

am
I destined to end up with precip again?

Not necessarily, because you wouldn’t be doing the same thing as you did before:

so I started dumping more soda ash (unbalanced) to the tank. I think I was at 125 cc alk and 25 cc of ca in pursuit of that effort. Since soda ash wasn't working, I started dumping kalk. And the whole thing started up there. Where my problems began.

You would ensure alkalinity was maintained at a proper range (7-11dKH) and then if you dose any alkalinity additives, especially high pH additives like calcium hydroxide (kalkwasser) or sodium carbonate (soda ash), you would dose it slowly, spread out throughout the day.

Kalkwasser especially needs to be dosed throughout the day. The higher the localized pH (from high doses in a small space with low flow), the higher the likelihood for precipitation. You need to mix in the solutions quickly, so dose it in a high flow area.

 

[Randy Holmes-Farley]

One other question I have been struggling with, is even if I go slowly in raising ph and alk after I break the cycle, am
I destined to end up with precip again? ie- will repeating the same dosing regimen with the same pH elevation result in the same outcome? I guess the answer will be it depends on the amount of surface poisoning.
Or should my goal be lower alk and pH until I get more coral load into the tank, at which point I can start going up on dosing again?

Not destined too, but if you push alk and or pH too much, especially with newish sand, the risk rises considerably.

 

[drtechno]

Got it.
Thanks for the responses. Will see how it goes.

Slowly ramping all the dosing down over the next couple days and thankfully my pH hasn't cratered and has been able to be kept 7.8-8... Alk hasn't dropped below 6.5 yet so that's good as well

 

[Miami Reef]

Got it.
Thanks for the responses. Will see how it goes.

Slowly ramping all the dosing down over the next couple days and thankfully my pH hasn't cratered and has been able to be kept 7.8-8... Alk hasn't dropped below 6.5 yet so that's good as well

How do you test for pH? If a probe, have you calibrated it with 7 & 10 pH solutions?

 

[drtechno]

How do you test for pH? If a probe, have you calibrated it with 7 & 10 pH solutions?

Ya, Apex pH probe.

Yes, I calibrated it with the 7 and 10... it was 3 months ago so maybe I should recalibrate now, given that I am going to rely on it as I bring everything back online again.

 

[Miami Reef]

Ya, Apex pH probe.

Yes, I calibrated it with the 7 and 10... it was 3 months ago so maybe I should recalibrate now, given that I am going to rely on it as I bring everything back online again.

That would be a good idea. Sometimes the calibration can go off for some reason. It can’t hurt to double check and make sure.

The reason I’m skeptical is with all that kalkwasser and soda ash, I would be surprised if the pH didn’t go up to 8.4. Even with high indoor CO2, I would still expect a large spike if dosing a lot at once.

I could be wrong, be it wouldn’t hurt to double check.

 

[QuickrdenU]

Thanks for this thread btw. I don’t have precipitation but with a similar new system, I’m hoping this helps me avoid it.

I’m dosing a small amount of baking soda and only 1000ml of kalk overnight. I’m scared! maybe rightfully so!

It sounds like the key is to ramp things up very slowly to let the system mature.

 

[drtechno]

Thanks for this thread btw. I don’t have precipitation but with a similar new system, I’m hoping this helps me avoid it.

I’m dosing a small amount of baking soda and only 1000ml of kalk overnight. I’m scared! maybe rightfully so!

It sounds like the key is to ramp things up very slowly to let the system mature.

Ya, your approach sounds right. I was hell bent on getting my tiny frags growing fast ASAP, which to me meant cranking pH and alk up as high as I could, and quickly before the corals arrived.

I am curious tho, how much alk coralline algae uses up, as I am just starting to get some signs of robust coralline growth which I hadn't seen before.

 

[QuickrdenU]

It sounds like it can drop the alkalinity quite a bit once fully established. Which is probably why I’ll be scraping it off my back glass when that time comes!

 

[drtechno]

Not destined too, but if you push alk and or pH too much, especially with newish sand, the risk rises considerably.

So I’ve let you the system drift down, and the alk has steadily been on a downward slope, currently measure 5.2 dkh and pH 7.6-7.8. I’ve been continuing my AWC of 1% per day, with the salt mix having a dkh of 7.

The exact alk trend (validated by 2 test kits) has been daily readings starting on the 19th of 6.3, 6.1, 5.8, 5.5 and 5.2. So can that be right that my newish system is using 0.3 dkh/day ?
or am I still precipitating in the sand ? (Doubtful now).

I’m thinking I should start dosing back up again slowly.

 

[BigMonkeyBrain]

So I’ve let you the system drift down, and the alk has steadily been on a downward slope, currently measure 5.2 dkh and pH 7.6-7.8. I’ve been continuing my AWC of 1% per day, with the salt mix having a dkh of 7.

The exact alk trend (validated by 2 test kits) has been daily readings starting on the 19th of 6.3, 6.1, 5.8, 5.5 and 5.2. So can that be right that my newish system is using 0.3 dkh/day ?
or am I still precipitating in the sand ? (Doubtful now).

I’m thinking I should start dosing back up again slowly.

Did you throw some dry ice in the tank ? I would not let my alk drop below 6.5 before I started dosing some form of alk.

I always wanted to weigh my aragonite sand after a few years and see if precipitation has keep up with dissolution in the low PH of the sand bed.

"Prediction is very difficult, especially if it's about the future."
Niels Bohr

Probably happens !

 

[Randy Holmes-Farley]

So I’ve let you the system drift down, and the alk has steadily been on a downward slope, currently measure 5.2 dkh and pH 7.6-7.8. I’ve been continuing my AWC of 1% per day, with the salt mix having a dkh of 7.

The exact alk trend (validated by 2 test kits) has been daily readings starting on the 19th of 6.3, 6.1, 5.8, 5.5 and 5.2. So can that be right that my newish system is using 0.3 dkh/day ?
or am I still precipitating in the sand ? (Doubtful now).

I’m thinking I should start dosing back up again slowly.

I'd use baking soda to maintain 6.5 dKH for a while. Moving up too quickly will restart the process.