Clumping sand and high alk/Ca usage

[Joe Rice]

My 150 gallon tank is suffering from "clumping sand bed" syndrome. In fact, much of my sand bed is now rock hard particularly around the base rock. The tank has been up for a year now and as far as I know I haven't really done anything unusual. The rock is BRS "Reef Saver" rock which I soaked in RO/DI water for several weeks before setting up the tank. The sand is Caribsea aragonite about 1/2 to 1 inch deep throughout.

My pH usually swings between 8.1 and 8.3. I keep my alkalinity around 8.5 and my Ca around 430. I have no detectable nitrates or phosphates.

But one other thing has always struck me as odd about the tank. It sucks down what I believe is an excessive amount of two-part dosing solutions - about 140 ml of the BRS alkalinity solution and about 220 ml of the BRS calcium solution per day. I have very few stony corals in the tank and the ones I have are mostly just frags (maybe 10 or so).

So I'm wondering if there's some chemical reaction going on that's pulling carbonate and calcium from the water and turning the sand bed into rock. And if so, why isn't this more common since I don't seem to be doing anything out of the ordinary?

Any insights would be greatly appreciated.

 

[clownsrcool]

I had that happen to me and never really got an answer as to why.

 

[250mixreef]

I had the same issue with brs 2 part I switched to a calcium reactor and problem solved

 

[cginter]

Same here. Using the same sand. On my first tank I used natures ocean live sand and did not have that problem. I've been taking the chunks out as replacing the sand when needed. I have no idea why it does it. As far as using excess amount, I dos 150ml/day of each cal and alk 2 part but I have a fair amount of sps

 

[Randy Holmes-Farley Verified Community Expert]

Here's my response from a similar thread today:

Clumping of sand may be purely abiotic, but may also be driven by biological processes, and most often happens with new sand.
Reduced precipitation can be reached with lower pH, alkalinity and to a much smaller extent, calcium, and higher magnesium, organics, and phosphate.

Fresh CaCO3 surfaces can be most prone to more precipitation. To break the cycle, it can be useful to stop dosing for a few days, let alk fall and precipitation stop, then restart with a much lower dose.

 

[Randy Holmes-Farley Verified Community Expert]

I had the same issue with brs 2 part I switched to a calcium reactor and problem solved

That's probably because the pH was lowered if you kept alkalinity the same. A simpler change might be to use baking soda (sodium carbonate) instead of washing soda (sodium carbonate).

 

[Joe Rice]

Same here. Using the same sand. On my first tank I used natures ocean live sand and did not have that problem. I've been taking the chunks out as replacing the sand when needed. I have no idea why it does it. As far as using excess amount, I dos 150ml/day of each cal and alk 2 part but I have a fair amount of sps

You have at least 10 times the amount of stony coral as I have in my tank which would seem to verify that my alk/Ca usage is indeed excessive.

 

[Joe Rice]

Clumping of sand may be purely abiotic, but may also be driven by biological processes...

Thanks for the reply. If it were due to some sort of biological process would it still be consuming carbonate and calcium from the water?

 

[Randy Holmes-Farley Verified Community Expert]

Thanks for the reply. If it were due to some sort of biological process would it still be consuming carbonate and calcium from the water?

I think it is, at least in part, calcification as opposed to a purely organic binder, so yes, it will consume them.

 

[TRock]

My apologies for reviving an old thread;

Around base rock where there is limited flow, and anoxic conditions in the sand bend below, I get calcification of my sanded. I believe this occurs when anaerobic bacteria is living under a high carbon, low nitrate environment. It's calcium carbonate sticking the sand together, but it's caused by bacteria. Opposed to an "organic glue" which happens to some people.

Thoughts?

 

[Randy Holmes-Farley Verified Community Expert]

My apologies for reviving an old thread;

Around base rock where there is limited flow, and anoxic conditions in the sand bend below, I get calcification of my sanded. I believe this occurs when anaerobic bacteria is living under a high carbon, low nitrate environment. It's calcium carbonate sticking the sand together, but it's caused by bacteria. Opposed to an "organic glue" which happens to some people.

Thoughts?

It's possible, certainly.

I think a lot of the time it may be abiotic preciptiation since it seems to happen most often in new, raw sand when folks have high pH and alkalinity (as when usign limewater/kalkwasser0.

Various types of bacteria and algae can cause conditions suited for calcium carbonate precipitation, especially photosynthetic organisms that take up CO2 and hence raise pH.

https://onlinelibrary.wiley.com/doi/full/10.1046/j.1365-3091.2000.00003.x

I'm not sure why a high carbon low nitrate environment would be especially suited to it, however. Do you have a hypothesis of why?

 

[TRock]

No Randy, I don't.
This is an unscientific assumption of mine based off of a few accounts I have read online that match my own.

I was hoping there would be a few others come in this thread and confirm the same situation.

As a result, I don't have a good basis for believing this at this point. I'm just trying to drum up some discussion.

 

[Randy Holmes-Farley Verified Community Expert]

OK, fair enough.

 

[Joe Rice]

Based on what I've read here and heard from other more experienced reefers (Greg Hiller in particular), I would do the following now if I were starting a new tank.

1. Buy "live" sand, not so much for the nitrifying action but because it seems like it might have a head start on getting a bio-film on the sand which might help to reduce nucleation sites where precipitation can get a foothold. I believe Greg once said that he rinses new sand in old tank water for a similar reason.

2. Run with low alkalinity, low calcium and high magnesium for a period of time and stir the sand occasionally (or get a bunch of nassarius snails) to, again, allow the sand to develop that bio-film during a period while the water chemistry is biased against precipitation.

 

[Randy Holmes-Farley Verified Community Expert]

I hadn't thought of the old tank water idea, but it's a good one.