Sand turning to rock

[pascal32]

I'm having problems with my sand bed turning into rock. I had a minor case of this in my display - then when cleaning the new SPS frag tank (on the same system), the entire sand bed (about 3-4 weeks old) was hard as a rock. I picked up one frag and the one and inch over came up up with it. I took some sand out and vaccumed the tank, now (a week later) I get back from the swap, go to put a new piece in the LPS frag tank and same thing. The LPS tanks (about 2 months old) doesn't seem to be as affected, only a few spots here and there, all near the edge.

The LPS tank has black sand (bag of wet sand "live sand") and the SPS tank was done out of dry reef sand.

levels:
CA (Salifert) 450
KH (Salifert) 9
MG (Salifert) 1400
Nitrate (Salifert) really low, as in i couldn't see a color shift
PO4 (Hanna ULR) 0.003066 PPM

the SPS tank has pretty good flow, the LPS tank is very low flow, decent turn over.

any thoughts?

 

[belgian_waffleman]

This clumping happens with the dosing of Calcium. I had the same issue. I no longer have a substrate in the front of my tank as I kept pulling the clumps out.

Waffleman

 

[Gravesj1s]

As far as I know theres a couple ways it can happen.One therory is that precipitaion occurs in the sediment fusing the grains of sand together.This can definately happen as some reefers have intentionaly done it to make reef rock using limewater or something similar.

Another theory is that bacteria produce glue like substances as a byproduct of denitrification ,this is seen mostly by someone using vinegar as it has to do with acetate.

Whatever the case ,I was only aware of it occuring when the sediment is still new-ish.The common opinion is once bacterial slime coat the sediment (maturing) ,its unlikely it will happen.

 

[tmz]

It's a combination of bacterial activity and precipitation. Here is a very good explanation by Boomer from the chemistry forum:



I think I have explained this before. In Sedimetentology we call this "Early Marine Diagenesis"

1. The local water in the SB develops a low pH from activity. This causes the dissolution. As dissolution continues the local pH, Alk and Ca++ begin to rise and reaches saturation, causing the precipitation of some CaCO3 around the grains "welding" them together.

2. Fresh new carbonate sands, like in a new tank, are not in equilibrium with the water. This causes the direct precipitation of calcite and often Hi-Magneisum Calcite on the the sand grains surfaces " welding " them together. There are many paper written on this and it is this that is more than likely what is happing in new tanks with new sand bottoms of carbonate sands.

3. Excessive Ca++ Alk and high pH can also cause this, as the sand favors more to precipitation in the SB, which will be even greater if the temp is a little higher there.

The above three produce a cement like clumping structure, where the grains can not be separated without hammer in hand.

4. Certain types of high SB bacterial activity produce organic "slimes / glues" that stick the sand grains together. In this case of SB clumping the grains can be pulled apart. The are more like a sticky cluey mess.



Forgot

Kalk with vinegar or other types of carbon dosing could make this worse where there may be more than one thing going on.


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An

 

[Gary Majchrzak]

re: sand clumping

re: sand clumping

I've discussed this with Randy Holmes-Farley (and others) before.

IME I've never had sand clump when dosing kalkwasser- even when dosing limewater to astronomical levels.
I've only ever had sand clump/cement together when (over)dosing liquid two parts.

 

[aww_419]

+1 Gary had the same problem a few years ago with liquid B-ionic, started making my own 2 part and cut down on the amount and havent had a problem since.

 

[Gary Majchrzak]

I don't know if I can find previous discussions but everyone that I know of that experienced sand cementing together was overdosing liquid two parts.......

 

[Gravesj1s]

That is interesting about the 2 part.

I have never used 2 part though. In my case I was dosing limewater to my sump,whitch had about an inch of carribsea special grade sand.Stuff turned as solid as concrete.Though it didn't happen in the display.

 

[naprestsleep]

I dose my kalk into my refug, and I just removed the sand bed from it. Was easier than I planned as it came up in large pieces. Interesting thread and I am find out more of why it happened.

 

[Gary Majchrzak]

limewater should be dosed into an area of good water movement.

Refugiums typically don't have decent water flow happening in them.

Dosing limewater into a refugium is a good way to kill whatever is taking refuge there

 

[pascal32]

I don't know if I can find previous discussions but everyone that I know of that experienced sand cementing together was overdosing liquid two parts.......

hmmm...how do you define "overdosing"? I dose quite a bit - 180ml of part 1 per day. I increase the dosing if I notice a trend down in the KH. Am I using an incorrect guide to adjust my dosing?

 

[tmz]

I've had some serious clumping and I dose only kalk( limewater/ calcum hydroxide) in 150 even small increments over a 24/7 cycle to a very high flow area.. I only ocassionally
( about once every ten days) add a little ( 1 tbspn for the 550 gallon system) baked baking soda very slowly to a high flow area. Clumping is more pronounced when alk is in the higher range( say over 11 dkh) but still occurs to a lesser extent at 9.5 dkh.

Overdosing kalk or carbonate/bicarbonate will certainly contribute to more clumping .

Boomer explained this in # 1 of his post.

1. The local water in the SB develops a low pH from activity. This causes the dissolution. As dissolution continues the local pH, Alk and Ca++ begin to rise and reaches saturation, causing the precipitation of some CaCO3 around the grains "welding" them together.


Perhaps this elaboration will help clarify the process.

The reference to activity ,he makes , refers to bacterial activity which lowers localized ph in the aragonite sand. Aragonite is mostly calcium carbonate. The temporary drop in localized ph engenders some dissolution of the aragonite sand and the extra carbonate alkalinity from this dissolution raises the ph back up causing a subsequent crystalization/precipitation of calcium carbonate cementing the sand grains together. Then more bacterial activity and so on.

The problem is that clumped sand will not allow adequate flow through it to maintain a healthy biological filter and may lead to anoxic areas forming in the sand bed .

 

[Gary Majchrzak]

hmmm...how do you define "overdosing"?

in this case I was using the term overdosing to refer to adding more supplements than necessary thus causing extremely high alkalinity and calcium levels.

It's (also) easy to overdose supplements by adding too much too fast- especially into an area of slow water flow.

 

[naprestsleep]

limewater should be dosed into an area of good water movement.

Refugiums typically don't have decent water flow happening in them.

Dosing limewater into a refugium is a good way to kill whatever is taking refuge there

I dose right at the return and there is a god bit of water movement. The refuguim was the best place I had for good flow and keeping the limewater from being directly sucked into a pump or my GFO reactor. Pods and such grow fine.

BUT I understand where your coming from.

 

[pascal32]

in this case I was using the term overdosing to refer to adding more supplements than necessary thus causing extremely high alkalinity and calcium levels.

It's (also) easy to overdose supplements by adding too much too fast- especially into an area of slow water flow.

thanks for the clarification - I don't believe this to be my issue as I dose with a slow dosing pump over 12 sessions per day into the return area of the sump which is pushing something over 1400GPH.

 

[pascal32]

I've had some serious clumping and I dose only kalk( limewater/ calcum hydroxide) in 150 even small increments over a 24/7 cycle to a very high flow area.. I only ocassionally
( about once every ten days) add a little ( 1 tbspn for the 550 gallon system) baked baking soda very slowly to a high flow area. Clumping is more pronounced when alk is in the higher range( say over 11 dkh) but still occurs to a lesser extent at 9.5 dkh.

Overdosing kalk or carbonate/bicarbonate will certainly contribute to more clumping .

Boomer explained this in # 1 of his post.

1. The local water in the SB develops a low pH from activity. This causes the dissolution. As dissolution continues the local pH, Alk and Ca++ begin to rise and reaches saturation, causing the precipitation of some CaCO3 around the grains "welding" them together.


Perhaps this elaboration will help clarify the process.

The reference to activity ,he makes , refers to bacterial activity which lowers localized ph in the aragonite sand. Aragonite is mostly calcium carbonate. The temporary drop in localized ph engenders some dissolution of the aragonite sand and the extra carbonate alkalinity from this dissolution raises the ph back up causing a subsequent crystalization/precipitation of calcium carbonate cementing the sand grains together. Then more bacterial activity and so on.

The problem is that clumped sand will not allow adequate flow through it to maintain a healthy biological filter and may lead to anoxic areas forming in the sand bed .

This makes sense. In my case it is likely the #2 is largely at play due to the "newness" of the affected sandbeds.

If I understand this correctly, some sand stirring snails such as Nassarius snails could be significant in preventing this as the PH would be neutralized with the tank water due to the disruption.

 

[tmz]

Keeping the sand well channeled ,is helpful to a sand bed and denitrifying bacteria as it ensures some flow and the prevention of anoxic areas as well as the the delivery of C,N and P which the denitrifying bacteria need to deeper areas. This is why benthic fauna is emphasized in dsbs.

 

[Gary Majchrzak]

I don't believe the recommended 'benthic fauna' for channeling includes Nassarius.
Quite frankly, I'm not a proponent of Nassarius in reef aquaria. It's my opinion that if you require Nass snails that you're probably feeding too much.

"Good" benthic fauna for a DSB (IMO) would include "regular" sandbed worms and pods.

Certain fishes (Wrasses, Gobies etc.) along with sandbed dwelling Holothurians (sea cukes) can be effective at keeping the uppermost layer of a DSB "stirred" but if you're sand bed is turning into cement there are other problems to address.

 

[Gravesj1s]

I prefer to stay clear of the dsb part of discussions.There are other parts indirectly that are worth mentioning though.Just wanted to point out that if stirring the sediment is what someone was looking to acheive ,then you should consider what kind of sediment you have.Gobies cant sift the larger stuff very well that alot of us use.

seacucumber worms do poorly in larger grained sediments and may even starve to death.They feed by ingesting the sand and cannot do this with the larger granual sized stuff.As far as I know they use fine grain sand something worth considering.Imo.

spaghetti worms dont survive well,if at all in the larger granual based substrate.As I recall they self mutilate trying to crawl through the substrate so they'd be a poor choice for anything but fine sand or smaller grain sediments.

I just thought it was worth pointing out as it seamed like sand stirrers were getting lumped together.

On a last note ,the larger granual based substrate ,ime anyway,if solidified will not breakapart without a hammer.Where as smaller sand grain sediment can be crumbled fairly easily in your fingers.

 

[tmz]

I prefer to stay clear of the dsb part of discussionsGraves,

Sanbed discussions can be abrasive , shifting and heated ; staying clear of them is wise unless you bring a big sand(BS) shovel and a pail of water and a sieve to sort out any gems that may be there.