Why does my sand bed keep turning into a brick?

[rjdudek]

You should check some of the common causes also. Read the article on this link:
http://www.ronshimek.com/deep_sand_beds.html
About para10 has a mention of glycocalices from bacteria. If you use Google you can find a number of mentions of sandbeds turning to "rock" as a result of this process.

 

[Greg Hiller]

Is this a particularly low nutrient system? Usually people have the most problems with this when they have a system with a lot of new sand and high calcium, alk, and pH. Usually the nutrients in a system tend to coat the new/clean calcium carbonate surfaces and then you don't have a problem because this stops the deposition of calcium carbonate on the surface of the crystal.

Are you sure the pH is 8 and not a lot higher?

 

[Greg Hiller]

>maintain my CA and Alk levels with a CA reactor<

Just saw this....I'm really surprised you are having this problem in a system with a calcium reactor due to the usually suppressed pH in such a system.

 

[stevenp]

Is this a particularly low nutrient system? Usually people have the most problems with this when they have a system with a lot of new sand and high calcium, alk, and pH. Usually the nutrients in a system tend to coat the new/clean calcium carbonate surfaces and then you don't have a problem because this stops the deposition of calcium carbonate on the surface of the crystal.

Are you sure the pH is 8 and not a lot higher?

I just checked the PH after the lights have been on all day and it was about 8.1 (Salifert and Milwaukee meter gave the same result). It doesn't seem to drop much at all overnight either.

At one point this was a very low nutrient system. I started with brand new sand and all dry rock that went through a bleach bath and several months of drying. Only fish were two baby bangaiis for the first several months. Alk may have been high too, can't remember.

But now the tank has been set up for a few years and has a decent amount of fish, not quite what I'd consider a high bioload, but certainly a decent bioload.

 

[stevenp]

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

The flow is high enough to make my 8" green tree coral lay down on the sandbed but not enough to blow the sand around. I am not running ozone.

 

[delta]

This can also happen when your system is boarding cyano or Dino they lay right beneath the surface of the sand and bascially smoothers your sand bed. Leaving a nice crust on the surface.
Do you have alot of air gas bubbles throughout the day or patched of cyano or Dino?
Cucumbers are a very useful tool along with a tons of flow, when this occurs .
More common with new cycling sandbeds

 

[Greg Hiller]

A little late now, but one thing you could try if you ever add new sand....suck some water out of a semi dirty tank into a bucket. Pour the new, clean sand through the water in the bucket. Let it sit in the bucket for a few days, maybe with an airstone to keep the water from going too low in O2. Stir the sand every few days. THEN add that sand to your tank. I'd think that the calcium carbonate surfaces would then be 'coated' and less likely to fuse. The points above about cyano, and diatoms may also be quite valid in that they are changing the chemistry in a very local way. I've never had it happen that way myself, so I'm reluctant to comment on it.

 

[rjdudek]

There is a test to determine if it is biologic or chemical in the article link posted above, why not try that and find out if it bacterial or calcium.

 

[loru1588]

There is a sponge that can bind the sand also. I had this trouble in several of the smaller (2 1/2 gallon) invert tanks when I was with Tropic Isle. Best thing I found was to remove all the sand and scrub the base of the rocks that touched the sand. Larger sand sifters like a sand sifter starfish or olive snails helped quite a bit.

Hope this helps,

Dan

 

[stevenp]

Do you have alot of air gas bubbles throughout the day or patched of cyano or Dino?

No dinos. A little bit of cyano but it's on the rock work and not the sand bed.

A little late now, but one thing you could try if you ever add new sand....suck some water out of a semi dirty tank into a bucket. Pour the new, clean sand through the water in the bucket. Let it sit in the bucket for a few days, maybe with an airstone to keep the water from going too low in O2. Stir the sand every few days. THEN add that sand to your tank. I'd think that the calcium carbonate surfaces would then be 'coated' and less likely to fuse. The points above about cyano, and diatoms may also be quite valid in that they are changing the chemistry in a very local way. I've never had it happen that way myself, so I'm reluctant to comment on it.

Good idea.

There is a test to determine if it is biologic or chemical in the article link posted above, why not try that and find out if it bacterial or calcium.

I think that's the same test I mentioned above. Soak the sand bricks in bleach (I said vinegar in my post, but meant bleach) and if it breaks up it's bound from bacteria. If not it's something else. Mine didn't break up.

There is a sponge that can bind the sand also. I had this trouble in several of the smaller (2 1/2 gallon) invert tanks when I was with Tropic Isle. Best thing I found was to remove all the sand and scrub the base of the rocks that touched the sand. Larger sand sifters like a sand sifter starfish or olive snails helped quite a bit.

Interesting. Can you describe what the sponge looked like?

 

[loru1588]

It was a pale cream or off white / gray in color. It kind of grew between the grains of sand like mortar between bricks on a minute scale. It wasn't noticeable until you went to stir the sand and as you mentioned, it was like a brick and came out in chunks.

 

[Greg Hiller]

>There is a sponge that can bind the sand also.<

Learn something new in reefkeeping everyday. Thanks for sharing.

 

[jbundas]

I used to have the same problem back in my kalk days. My mag was also low at the time. Once I switched to a Ca reactor and kept a better eye on my chem parameters (which are about the same as yours) I never had another problem. I'd consider stopping the "top off with 100% saturated limewater" and see what happens.