Alk dropping drastically low

[rosebud161616]

Background:
I got my mom into reefing a while back and she has now worked her way up to a 60 gallon cube. As of about a week ago she has had an extremely hard time keeping her alk up. So much so that I was positive she was doing something wrong.

I am currently working during the week in Cincinnati (where my mom is) and going home on the weekends to Columbus.

Tank:
60 cube with a 20 gallon sump
20% water change done weekly with reef crystals
saturated kalk solution dosed at time of water change as needed
GFO reactor running BRS high capacity GFO
NAC cone skimmer
MP40

Problem:
Last week her alk had dropped down below 8dKh and she has been working on raising it, per my instruction and as she has done in the past, using kalk solution. She told me she was adding a gallon of solution each day and it wasn't making a difference. I went over on Thursday and inspected the tank to find that she is testing correctly and is adding the kalk correctly, but it was not raising her alk.

I told her to continue trying to raise/maintain over the weekend and I would bring back more test kits on Monday. She added gallon after gallon of kalk solution over the weekend. I got there tonight to find that her alk was down to around 3.8 dKh. I tested her magnesium, sure this was her problem, and it was fine at 1260ppm. I tested her Calcium thinking possibly the ratio was way out of whack but it was fine at 420ppm.

I am absolutely stumped at what is causing this drop! The only thing that has changed is she swapped out her GFO for fresh around the time that this started. Can GFO have any sort of change on Alk?

I turned off the GFO reactor and raised her tank back up to 6dKh. I instructed her to test again in the morning and report back. If it was at 6, then I asked her to go ahead and add another 1/2 gallon of solution to bring it to 7dKh and I would come back over after work.

I also asked her to save some saltwater from her water change so I could test. She kept it moving with a small pump over the weekend and I tested tonight. The alk on it was 12dKh.

The alk kit that we are using is a Salifert and tested it against the reference solution. The test came back spot on.

Any thoughts on what could be causing this? She lost one wrasse over the weekend and the other was looking very rough tonight. She's trying so hard with this tank and I hate to not have a better answer for her.

I thought possibly her cats have been peeing in the tank (though she assures me this could not be the case) which would lead to an acid dropping her alk. She setup empty milk jugs on top of her tank to see if they get moved (proving the cats are getting up there).

The only other thing I can think to do is to try to source some 2 part (just the alk portion) down here tomorrow. Perhaps adding the kalkwasser is adding too much calcium and causing calc/alk to precipitate out together? Maybe adding just the alk portion of 2 part will make a difference?

Sorry for the long post, but any help is appreciated!

 

[plankton]

Reef Crystals runs high alk (13 dkh) typically. If you are doing 20% weekly water change I find it hard to believe that you have a bioload that can pull down 13 dkh down to 6? dkh less than one week.

What are your other param? Ca, Salinity, Magnesium, nitrite, nitrate?

How much kalkwasser top-off do you add per day? Although the impact to alk/ca is rather minor with CaOH, since so little is actually dissolved into RO/DI. If you really want to raise alk the easiest way is by adding baking soda dissolved in RO/DI. Use one of the reef calculators to calculate how much virgin Baking Soda (slighly lowers pH) or baked baking soda (slight raises pH) to figure how much baking soda to raise however much dkh per day. Like this one. But, don't raise the Alk more than 1dkh per day or risk stressing your corals. Fish normally are not sensitive to alk changes.

 

[bertoni]

Many tanks consume alkalinity at the rate of 2-3 dKH per day. Limewater often can't keep up with the demand. I agree with trying a 2-part for a while. There are DIY 2-parts to save money over the long haul, although some people prefer a calcium reactor.

 

[rosebud161616]

Reef Crystals runs high alk (13 dkh) typically. If you are doing 20% weekly water change I find it hard to believe that you have a bioload that can pull down 13 dkh down to 6? dkh less than one week.

I even tested the reef crystals to make sure that she wasn't doing water changes with something low in alk. It came out at 12.4 dKh. I agree that I just don't believe that her tank is consuming alk that fast. She isn't overly stocked and doesn't have a ton of stonys. Here is what she has:

2 monti digis
small monti cap
1/4" nub of setosa
3-4 heads of hammer
3-4 heads of duncan
3-4 heads of dendro
small wellso brain
a small single head blasto

What are your other param? Ca, Salinity, Magnesium, nitrite, nitrate?

The Calcium was 420, Salinity 1.025, Magnesium 1260, ammonia 0, nitrite 0, I did not test nitrate.

How much kalkwasser top-off do you add per day? Although the impact to alk/ca is rather minor with CaOH, since so little is actually dissolved into RO/DI. If you really want to raise alk the easiest way is by adding baking soda dissolved in RO/DI. Use one of the reef calculators to calculate how much virgin Baking Soda (slighly lowers pH) or baked baking soda (slight raises pH) to figure how much baking soda to raise however much dkh per day. Like this one. But, don't raise the Alk more than 1dkh per day or risk stressing your corals. Fish normally are not sensitive to alk changes.

She is not adding kalkwasser through top-off per say. She is adding it just as needed to raise her alk (per the BRS calculator for saturated lime solution), which this past week has been significantly more than has been needed for top off. Her ATO is just turned off at this point. She has added gallons a day to try to raise it.

Many tanks consume alkalinity at the rate of 2-3 dKH per day. Limewater often can't keep up with the demand. I agree with trying a 2-part for a while. There are DIY 2-parts to save money over the long haul, although some people prefer a calcium reactor.

I have had my tanks use that kind of alk in a day before, but it was a heavily stocked (and a smaller tank) SPS tank. I used kalk ATO for a long time and got to the point where it just wasn't keeping up. I had to switch dosing 2 part. But it was never a drastic change like this, and I never saw the alk ever get this low. Corals should use less alkalinity as the alkalinity drops and more as the alkalinity is raised into the normal range. There should be a point where the corals stop growing/dying that causes the alk to level off. It doesn't seem that her tank is getting to this point making me think something else is causing this drastic drop.

I will try to source some 2 part tonight as my mixes are up in Columbus. I think I will go ahead and work on raising her mag a bit to see if it will help hold any more alk just in case this is some sort of precipitation issue.

 

[Finland]

She has added gallons a day to try to raise it. .

Gallons per day of Kalk in a 60 gall tank?? How much evap does she have?? I would think that would raise the pH thru the roof causing precipitation plus mess with the salinity. I would suggest stopping kalk for a few days and using 2 part to get your parameters to where you want them. Add the 2 part slowly, preferably with a doser. Once you get the parameters stabilized, then start up with kalk.

 

[bertoni]

I had tanks with no stony corals at all that consumed 2-3 dKH per day, just due to coralline growth. If the magnesium kit is accurate, adding a bit of magnesium is fine, but won't help.

 

[rosebud161616]

That's a great point. She is getting a large bloom of coralline. I'll work on sourcing 2 part today and get her started. Sounds like it's time I get her into a controller and a doser...

 

[plankton]

Yeah, it is going to be difficult to meet that alk demand via kalkwasser...

Baking soda is the obvious choice near term - but you want it to be balanced with Ca. Get the Alk where you want it (8 dkh, 9, 10dkh whatever) then wait 24 hours and measure alk again to see what the tank consumes in 24 period. Then, you can manually dose two-part per day until you get your dosing pumps.

PS Salifert Alk kits tend to be a little 'off'. So, personally I wouldn't run a tank at 8 dkh as read by salifert and would run at least 9 - I run 10dkh.

Good luck with the tank.

 

[Daimyo68]

I was in the same boat at one point, couldn't keep the alk up, using reef crystals, having water tested at 3+ places.

Pretty much followed what everyone said and got my alk to 10dKh and checked it the next day with no dosing. It had dropped to 7dKh.

I started dosing Alk (Baked Baking Soda) and was dosing what seemed to be too much every day, and was really worried that I was going to spike the system. It was pretty amazing to see how fast the little 50g was taking Alk down 3-4dKh every 24 hours.

Been dosing Randy's recipe 1 since then and have stable numbers.. finally.

Here's the link for his recipe. Read through it before deciding on recipe 1 or 2. I use Arm and Hammer Baking Soda from the local supermarket, and get my Calcium powder from BRS.

http://reefkeeping.com/issues/2006-02/rhf/index.php

 

[rosebud161616]

Thanks guys. I found some 2 part for her last night and dropped it off. Corals were looking pretty terrible and both of her wrasses are gone. She had added another gallon of kalk that morning which maintained 6 dKh. Hopefully it will be a little easier for her to stay on top of her alk demands.

 

[troyman]

2 much calcium can cause a depleation of alkalinity

 

[Daimyo68]

She had added another gallon of kalk that morning which maintained 6 dKh

A gallon of Kalk? What is the pH at?? If she actually added a full gallon then her pH has got to be off the charts. What kind of test kits is she using?

I would stop the Kalk at this point until you make the Alk solution and get that settled at a number she/you are happy with. Then start the Cal and get them balanced out.

 

[bertoni]

Um, she's adding Kalkwasser as a supplement? That's no good. It needs to be dripped very slowly, and the amount is limited to the evaporation losses of the tank.

 

[troyman]

it wont even saturate in the water just by dumping it in

 

[rosebud161616]

No worries guys, this isn't my first rodeo. She is stopping the kalk dosing anyway and starting the 2 part (well 1 of the 2 parts for now.)

 

[tmz]

IME calcium hydroxide (kalk) can meet more demands than it often gets credit for if you spread out the dose over the course of the day or at least break top off needs into 4 or five doses an hour apart.