Why does my sand bed keep turning into a brick?

[stevenp]

Probably 6 months ago I removed my Carib-Sea sand bed in large chunks because it had solidified. I attributed it to high alk (12-13dkh), so I lowered my alk and waited until it stabilized to add new sand.

I replaced the sand bed with fresh Carib-Sea. Things were just ducky for several months. I started to notice it hardening again in several places. Today I reached in the tank and removed massive Carib-Sea "bricks" (the new sand was purchased at the same time as the old sand. Is it possible there was something wrong with the sand?).

What's interesting is that it always seems to solidify in the same areas of the system. In the display it hardens where the flow is strongest over the sand bed, and it also seems to harden in the sump where there's an excess of air bubbles.

Parameters, which always seem to be pretty stable (I check my water every week or two):

CA = 426ppm (Hach)
KH = 9.5dkh (Hach)
SG = 1.025sg (refractometer)
MG = 1427, but has been as high as 1520 (Hach)

Phosphates tested 0 with Hanna photometer (running GFO 24/7).

I use regular TM salt and maintain my CA and Alk levels with a CA reactor. I top off with 100% saturated limewater.

What the heck, yo? Could it be the Mg?

 

[Aquadiva]

How are your sandbed critters?

Got enough things stiring the sand?

 

[stevenp]

How are your sandbed critters?

Got enough things stiring the sand?

I think so. The tank has been up for 3-4 years so there's plenty of life in it. For sifting-type critters I have:

- Probably a dozen or so Nassarius snails. They actually grew coraline algae on their shells because they could no longer get into the sand .

- Pistol shrimp and goby (these guys move a TON of sand)

- Wrasse that buries himself from time to time

- School of bar gobies that have a den in the sand

- Various bristle worms, pods etc.

 

[Aquadiva]

I was thinking more along the lines of the tiny critters. You said you replaced the sandbed, which is like starting over. Many new sandbeds have this problem I believe because of lack of bacteria...

Here, he said it better than I....

http://www.reefcentral.com/forums/showthread.php?s=&threadid=1436851&highlight=clumping+sand

Look at the first reply

 

[stevenp]

I added two large cupful's of sand from two established systems when I started the tank years ago. I would think that there is plenty of life in there. I was thinking more along the lines of a chemistry problem with my parameters/dosing etc. I suppose anything is possible though.

That picture on the 2nd page, that's exactly what I'm pulling out of my tank - and it sucks.

I remember reading that soaking the bricks in vinegar will tell you if it's a bacteria problem. If the sand breaks up, it's bacteria. If it doesn't, it's not bacteria. Mine didn't break up in vinegar.

Any ideas as to why it would be occurring in areas of high flow? That RC post suggests that low flow is a problem, but my problems are occurring in high flow areas.

 

[stevenp]

I should clarify that I didn't replace the sandbed entirely. I only removed the bricks and added some fresh stuff in its place. The same areas are now hardening again.

 

[Sokretys]

Wow. Very strange...Exactly how much flow are we talking about in the high flow areas? Are you running ozone?

You could try wetwebmedia.com...and write directly to Bob Fenner. Id search around on the site a bit for he doesnt care too much for answering questions that have already been answered and posted on the site. Often times there is too much info on wetweb. but id say try looking there and if you dont find anything useful...email wetweb but direct your question to Mr. Fenner.

Goodluck...

 

[stingythingy45]

"I top off with 100% saturated limewater.

What the heck, yo? Could it be the Mg?"

I would guess it's the limewater.
I've had my Mg. up around 1500 for almost a year and have had no problems like you describe.

 

[Miller]

I would like to know what causes this as well. I get areas in my sandbed that turn into bricks.

 

[ReeferMedic]

I believe it has something to do with high kh and ca. Maybe Greg will cime in on this. He posted a response to a similar post quite a while back, but I can't recall what exactly he said.

 

[Miller]

Paging Greg......Greg Hiller please report the the "Why does my sand bed keep turning into a brick?" thread.

I'd like to know why.....I have not really had high Alk or Ca.

 

[stevenp]

You guys could be thinking of my last thread about this.

At that time I attributed it to either high Kh or lack of life in the tank. This time around things are a bit different, so I now consider it a mystery. I'm really stumped why this is happening in my system.

I'm pretty close to saying 'the hell with it' and running bare bottom.

 

[Moe_K]

It happened in my tank when my alk and calcium were too high.
I'm thinking the combo being out of whack is the key.

Greg? Randy? Anyone? Buehler?

 

[Aquaman_68]

What you describe above usually means you have been running a lower ph than desired & due to this the ph of the sand is lower than optimal . This can cause the calcium carbonate (sand) to melt just like it does in a calcium reactor. As the liquid calcium starts to rise and hit the higher PH, it turns back into a solid and bonds your sand together. The more of the top layer of sand that gets bonded together, the lower the O2 level of the deeper sand will get and the problem will get worse. This enviroment is a perfect place to create hydrogen sulfide from the anerobic bacteria due to the zero 02 levels the hard pan creates.

If the level of hydrogen sulfide gets too high & you stir the sand it's like dropping a sulfide bomb into your system!!

FWIW....Hydrogen Sulfide will look like black spots in the sand when looking thru the glass at the sandbed..


Another note:
Adding Liquified Ca to the water under low flow can cause the same thing as well...The calcium percipitates into the sand from low flow or even over saturation as well. (which is what I think you actually may have experienced Moe)

Hope you understand without the exact chemical equation or formula added!!!


Hope you can grasp the concept without the chemical formula of this reaction taking place!!

Formulas bore me...

 

[wsonner]

What you describe above usually means you have been running a lower ph than desired & due to this the ph of the sand is lower than optimal . This can cause the calcium carbonate (sand) to melt just like it does in a calcium reactor. As the liquid calcium starts to rise and hit the higher PH, it turns back into a solid and bonds your sand together. The more of the top layer of sand that gets bonded together, the lower the O2 level of the deeper sand will get and the problem will get worse. This enviroment is a perfect place to create hydrogen sulfide from the anerobic bacteria due to the zero 02 levels the hard pan creates.

If the level of hydrogen sulfide gets too high & you stir the sand it's like dropping a sulfide bomb into your system!!

FWIW....Hydrogen Sulfide will look like black spots in the sand when looking thru the glass at the sandbed..


Another note:
Adding Liquified Ca to the water under low flow can cause the same thing as well...The calcium percipitates into the sand from low flow or even over saturation as well. (which is what I think you actually may have experienced Moe)

Hope you understand without the exact chemical equation or formula added!!!


Hope you can grasp the concept without the chemical formula of this reaction taking place!!

Formulas bore me...

Very nice and fascinating. It constantly amazes me that we are able to keep anything alive in our tanks with all of the factors involved. Great explanation.

Wes

 

[Aquadiva]

Way to go B ---

Nice explaination... especially without all the chemical reaction stuff

Maybe the Mods could look to this one for a sticky. It seems to come up often, especially with new tanks.

 

[SteveDola]

"FWIW....Hydrogen Sulfide will look like black spots in the sand when looking thru the glass at the sandbed.."

B, I have 1 of those black spots in my sandbed-only about the size of a quarter. should I stir it up to release the sulfide so it doesnt continue to build up? My sandbed isnt hard but the black spot is a low flow area...maybe thats a contributing factor. My system should be able to handle a small disturbance like that...dont you think?

 

[Aquaman_68]

"FWIW....Hydrogen Sulfide will look like black spots in the sand when looking thru the glass at the sandbed.."

B, I have 1 of those black spots in my sandbed-only about the size of a quarter. should I stir it up to release the sulfide so it doesnt continue to build up? My sandbed isnt hard but the black spot is a low flow area...maybe thats a contributing factor. My system should be able to handle a small disturbance like that...dont you think?

Just poke an acrylic rod thru it & let some escape from the center when you pull the rod back out...

 

[ReeferMedic]

What you describe above usually means you have been running a lower ph than desired & due to this the ph of the sand is lower than optimal . This can cause the calcium carbonate (sand) to melt just like it does in a calcium reactor. As the liquid calcium starts to rise and hit the higher PH, it turns back into a solid and bonds your sand together. The more of the top layer of sand that gets bonded together, the lower the O2 level of the deeper sand will get and the problem will get worse. This enviroment is a perfect place to create hydrogen sulfide from the anerobic bacteria due to the zero 02 levels the hard pan creates.

If the level of hydrogen sulfide gets too high & you stir the sand it's like dropping a sulfide bomb into your system!!

FWIW....Hydrogen Sulfide will look like black spots in the sand when looking thru the glass at the sandbed..


Another note:
Adding Liquified Ca to the water under low flow can cause the same thing as well...The calcium percipitates into the sand from low flow or even over saturation as well. (which is what I think you actually may have experienced Moe)

Hope you understand without the exact chemical equation or formula added!!!


Hope you can grasp the concept without the chemical formula of this reaction taking place!!

Formulas bore me...

Yeah, what he said. Nicely put B.

 

[stevenp]

Thanks, Brian. My PH usually stays around 8.0 overnight, and naturally a bit higher during the day. I suppose it's possible that it was low for a while and I just didn't know it.