Sand bed leaching alkalinity?

https://www.triton.de/en/

Nick Steele

Valuable Member
View Badges
Joined
Apr 28, 2019
Messages
1,180
Reaction score
1,097
Location
Port St. Lucie
Tank status
Nuvo 20
2 ai 16hds
2 jebao sow4
South seas caribsea rock
Carina sea specia grade sand
2 clowns
7 hermits
5 trochus snails

I’ve always had some issues with weird increase in alk. I would get a small drop over the course of one week do a water change (turkey baste the sand and rock) and over the next few days I would get a .5-1.5 dkh rise in alk. I did have a bad batch of salt that would mix at 8-12 dkh that I have since gotten rid of and new salt will mix at 8.4 every time now. I had my alk at 8.8 a few weeks ago but is now at 9.8 again. Also I do use rodi unit to make my water at 0tds.

Is it possible that my sand bed could be leaching alkalinity?

If so would it be detrimental to remove the old sand bed and leave it bare bottom for a little while then add new sand back in?
 
BRS

xxkenny90xx

2500 Club Member
View Badges
Joined
Apr 2, 2019
Messages
3,683
Reaction score
4,419
What kinds of corals do you have in the tank? Removing the sand is fine but I'm not sure I see the point if your just gonna put new sand in??
 

Randy Holmes-Farley

Reef Chemist
View Badges
Joined
Sep 5, 2014
Messages
41,310
Reaction score
29,569
Location
Arlington, Massachusetts, United States
Tank status
Nuvo 20
2 ai 16hds
2 jebao sow4
South seas caribsea rock
Carina sea specia grade sand
2 clowns
7 hermits
5 trochus snails

I’ve always had some issues with weird increase in alk. I would get a small drop over the course of one week do a water change (turkey baste the sand and rock) and over the next few days I would get a .5-1.5 dkh rise in alk. I did have a bad batch of salt that would mix at 8-12 dkh that I have since gotten rid of and new salt will mix at 8.4 every time now. I had my alk at 8.8 a few weeks ago but is now at 9.8 again. Also I do use rodi unit to make my water at 0tds.

Is it possible that my sand bed could be leaching alkalinity?

If so would it be detrimental to remove the old sand bed and leave it bare bottom for a little while then add new sand back in?

Sand beds very slowly dissolving is real, but rarely any problem since it is far lower than the demand in most tanks, and it won't happen at uneven rates like you suggest. Just a slow steady dissolution. Live rock likely does too.
 
OP
Nick Steele

Nick Steele

Valuable Member
View Badges
Joined
Apr 28, 2019
Messages
1,180
Reaction score
1,097
Location
Port St. Lucie
Sand beds very slowly dissolving is real, but rarely any problem since it is far lower than the demand in most tanks, and it won't happen at uneven rates like you suggest. Just a slow steady dissolution. Live rock likely does too.

Okay thanks! Guess I won’t go and rip my sand bed out quite yet then.
 

Dan_P

Valuable Member
View Badges
Joined
Sep 21, 2018
Messages
1,655
Reaction score
1,519
Sand beds very slowly dissolving is real, but rarely any problem since it is far lower than the demand in most tanks, and it won't happen at uneven rates like you suggest. Just a slow steady dissolution. Live rock likely does too.
What is the rate of dissolution? 1% per year? 0.1%?
 
Fritz

GlassMunky

Valuable Member
View Badges
Joined
Jan 30, 2014
Messages
1,823
Reaction score
2,103
Location
Philly
Yes that can happen. Here’s another thread where it goes into details
 

GlassMunky

Valuable Member
View Badges
Joined
Jan 30, 2014
Messages
1,823
Reaction score
2,103
Location
Philly
What is the rate of dissolution? 1% per year? 0.1%?
My tank was raising by 0.1-0.2dKh per day... 210G tank with 65g sump.

I’ve since gone through and manually cleaned the sand and the following day the ALK raise stopped....

I can’t think that’s a coincidence....
 

Randy Holmes-Farley

Reef Chemist
View Badges
Joined
Sep 5, 2014
Messages
41,310
Reaction score
29,569
Location
Arlington, Massachusetts, United States
What is the rate of dissolution? 1% per year? 0.1%?

Some experienced reefers with long term tanks (e.g., Larry Jackson) added his sand back every few years, so in his tank it seems like 5%? Something on that order of magnitude. May vary a lot with sand surface area, water flow, deteritus accumulation in the sand, etc.
 

Nano sapiens

Valuable Member
View Badges
Joined
Apr 25, 2010
Messages
1,393
Reaction score
1,641
Location
Northern California
In the 12+ years of running my small system I've replaced about 5-10% of the aragonite substrate (Kalkwasser used exclusively).

I've been seeing a few threads lately regarding this issue of either stalled or rising alk with no intentional external means of supplementation. I just had a similar experience where I was attempting to let alkalinity drop from 12.5 dKh (faulty test kit) to 9 dKh by reducing KW usage in my ATO. As I steadily reduced KW over a few days, I noticed that alk was dropping much more slowly than expected and when I stopped KW completely the system stayed at 10.5 dKh for nearly a week with only RO for topoff. Complicating matters, I had also reduced lighting intensity by about 7% during this period to reduce stress on a few SPS corals that had suffered due to the higher alk.

A thorough cleaning of the sand bed, a 20% WC for the week and opening windows to get some fresh air for a short period each day in the house and the alk dropped much more quickly over a day or two to my intended 9 dKh. Consequently, I had to start KW again to maintain the current level.

I've had similar lowered KW usage events happen many times over the last 12 years, but never as extreme as this year. And interestingly, these events have typically occurred at the end of autumn/beginning of winter.
 
Last edited:
Top Shelf Aquatics

Dan_P

Valuable Member
View Badges
Joined
Sep 21, 2018
Messages
1,655
Reaction score
1,519
Some experienced reefers with long term tanks (e.g., Larry Jackson) added his sand back every few years, so in his tank it seems like 5%? Something on that order of magnitude. May vary a lot with sand surface area, water flow, deteritus accumulation in the sand, etc.
Not sure anyone would notice a 5% loss of sand.

Let’s assume aragonite sand dissolves. To calculate a daily alkalinity increase, let’s assume we have an aquarium with 1.45 lb sand per gallon. What daily alkalinity increase would we see for various annual percent sand bed dissolution rates? Check out the plot below.

The notion of a dissolving sand bed might have merit. It is still only supported by anecdotal evidence, but an idea worth looking into.

0E26325E-6BFE-4199-8DB9-1471BA1A752B.png
 

Dan_P

Valuable Member
View Badges
Joined
Sep 21, 2018
Messages
1,655
Reaction score
1,519
On this thread? and here: https://www.reef2reef.com/threads/alkalinity-rising-without-dosing-possible-causes.731986/page-4

I am suffering from this with a tank that is only 8 months old.. I have been going nuts..

S.
O, sorry! Obviously I need to pay better attention.

If you were to remove a sample of sand from your system and place it a sample of aquarium water, aerating the water if practical, would this sample water alkalinity increase like it does in the aquarium? I am looking for ways we can prove it is the sand.
 
Budmans

Randy Holmes-Farley

Reef Chemist
View Badges
Joined
Sep 5, 2014
Messages
41,310
Reaction score
29,569
Location
Arlington, Massachusetts, United States
Hi Randy,

Thanks for the response, is it safe to use silica sand in reef aquariums then?

S.

Some release of silicate will happen, but generally not a problematic level. I’d use a natural sand, which is naturally well washed, not ground up stuff like for sand blasting.
 

Simbol

New Member
View Badges
Joined
Jan 1, 2021
Messages
5
Reaction score
0
Location
UK
Hi Randy Thanks, I performed an experiment and:

1) Cleaned my coarse aragonite sand.
2) Increased flow of the tank by 30-40%
3) Dropped my Gyres about 7 cm closed to the sand bed to increase flow around it.
4) Increased aeration in the living roon to raise PH.

These combined gave me Alk drop for the first time.. so clearly the issue is low PH zones in the sand bed.. my automatic KH tester (KH keeper, it test every 2 hours) is confirming my Alk raises between 4am to 12pm when my tank PH is below 8.1. I am now looking now to install a CO2 scrubber to keep PH higher and improve the situation.

I want to thank everyone for all the imput on these forums, it really helped me to understand the cause of the issue and how to attack the symptons to improve the situation!

Regards,
Raul from UK
 
https://www.triton.de/en/

Do you have reef tank aspirations and visions?

  • Yes (please tell us what in the thread)

    Votes: 118 84.9%
  • NO

    Votes: 19 13.7%
  • Other (please explain)

    Votes: 2 1.4%

Online statistics

Members online
959
Guests online
3,772
Total visitors
4,731
Hanna
Top