Can Aragonite peg alk ?

[Barks]

Hey all
Been fighting cyano for years.
When I set up my current tank 4 or 5 years ago I bought all the live rock from an lfs that was about to move. They gave me a really good discount as they said it would save them moving the rock and assured me the filtration was still on although it looked dirty to me.
I’ve had so many problems sps lasting a few months and then rtn.
Nearly gave up a few times.
Anyway.
I’ve recently done 3 50% wc.
Tried mb7. Nothing.
Tried dr Tim’s nothing.

I figured it may be a bacterial issue killing the sps so.
Last resort used chemiclean and it removed all the cyano in 48 hours and 3 weeks later it’s still gone. Tank looks great. Sps colouring back up.
Now the tanks clean I added some nice white sand.
9kg aqua natural course aragonite.

a few days After adding it my alk has dropped from 8.5 to 7.3 and seams to be pegged there. ??
I have tripled my alk dosing to test and no change what so ever still 7.3.

Is this possible.

Parameters before sand.

Temp 25
Sg 35
Alk 8.5
Ca 425
Mg not tested need new test kit.
Po4 0.03
No3 20
Ph 8.2

I would have thought if anything the alk would have risen slightly but only if ph dropped otherwise the sand won’t dissolve.

Any ideas.

Cheers barks

 

[taricha]

I would have thought if anything the alk would have risen slightly but only if ph dropped otherwise the sand won’t dissolve.

true.

One possibility that might actually be happening is that your nice new white sand added a bunch of fine particle aragonite spread around the system.

clean aragonite particles and surfaces can act as sites for precipitation from the water - which can lower alk. Old rocks and sand covered in organics are more stable and don't trigger precipitation like that.

 

[Randy Holmes-Farley]

At pH 8.2 and calcium of 425, aragonite exposed to that water will not dissolve unless the alkalinity is below 2 dKH.

As taricha notes, it can act as a seed crystal for more precipitation of calcium and alk, consuming alkalinity, until the surfaces become coated with phosphate, magnesium, bacteria, organics, etc. The higher the pH and alk (and calcium), the faster that process goes.

 

[Mikeltee]

I have a little cyano going on as part of new tank syndrome. It was bad at one point so I blew all the rocks off with a 500gph powerhead and used a 10u filter sock. Then I dosed coral snow mixed with MB7. After a couple weeks, the cyano was gone. I continued dosing the coral snow + MB7 for a month and there was no signs of cyano. I stopped a couple weeks ago and the cyano is returning. Coral Snow + MB7 will now be part of my weekly maintenance schedule. I also added a couple of gyre pumps thinking that there wasn't enough flow and the reason for cyano, but that was not the case.

In my 15 years of reefkeeping, I had cyano 3 times and chemiclean wiped it out within 24 hours. The last time i used it, I got dinos. From now on, when I address issues, I will take the slow path as rapid changes can lead to more significant problems in this hobby. This is where I learned about CS+MB7:

https://www.reef2reef.com/threads/extreme-water-clarity-and-cyano-eradication-made-easy.916381/

 

[Barks]

Thanks all.
Increased it again and still 7.3.
No precipitation.
I’m going to check mg tomorrow and if it’s ok work out what I need to raise it 1 dkh and dump it in over 24 hours.
Barks

 

[Dan_P]

Thanks all.
Increased it again and still 7.3.
No precipitation.
I’m going to check mg tomorrow and if it’s ok work out what I need to raise it 1 dkh and dump it in over 24 hours.
Barks

If you can, remove a sample of aquarium water and adjust the alkalinity. This will confirm that outside the aquarium, you are able to obtain the desired results. Then, if you are feeling energetic, add some sand from the aquarium to the adjusted sample to test whether it is causing the alkalinity decline.

 

[Barks]

Hi Dan.
I did consider that and I think that’s the next step because today I added 10g of sodium hydrogen carbonate which should have raised the alk from 7.3 to 8.5 and it did nothing.
So I’ve stopped dosing to see if it drops any and will remove some water tomorrow and try it out of the tank.
Cheers
Barks