kalk hardening the sand

[thien]

Ok, so I've been dabbling with some kalk and I read that if it is dosed too quickly, it will harden the sand. So I'm poking around the other day and there's a spot where the sand is rock solid! Did I just screw it up? Should I try to break it up?

[MalHavoc]

This is why I usually recommend that people who are first setting up their tanks make sure to soak the sand going into their new tank in a bucket of water change water for a few days so bacteria gets a chance to coat the grains of sand with some slime coating.

Aragonite oolitic sand is mostly calcium carbonate. Your water is high in carbonates, and you're providing an ideal environment for precipitation onto these sand crystals by adding tons of calcium in a high pH environment. If you're not careful, you'll end up making a brick.

Also, watch your tank's pH very carefully. I doubt you'll be able to break up the clump of sand very easily, but if it's just a small lump of sand, removing it and replacing it with new sand might not be a bad idea.

[john rock]

THIEN, how are you adding the KALK? and do you really need it. While KALK is great for SPS/LPS and large tanks with clams and tons of inverts,I find it basicaly not necessary for small tanks with mostly softies and the odd LPS. It should be premixed in fresh water and let settle so that the clear liquid is ''dripped'' into the sump area. If no sump, you have to be even more carefull as it could cause a ph jump in the immediate area or entire tank possibly killing everything! It needs to be diluted quickly before entering the tank[sump works best]. How are you adding and why? are you experiencing large ca/alk/ph swings?

[thien]

uh oh. I thnk I'm going to be in trouble.:ummm: here goes...

I'm adding the kalk via the kalk slurry method as described by Anthony Calfo on the Wet Web Media site. Basically, I add less than 1/4 tsp to about 1.5 cups of RO water. I swirl it around for about 30 seconds and I pour it in a little at a time in the tank in front of the PH over about 1 minute. The catch is this is safe as long as the PH spike is NOT greater than 0.2 and I measured this using my PH pen. And I do this in the morning before the lights come on.

I did this for about 3 weeks. I found that my levels for Ca and alk have been very stable (much better than before when I would use some Turbo calcium and buffer separately). And my corraline algae has increased. I only have some zoanthids, mushrooms, green star polyp, a big finger leather, a toadstool and a big candycane. So no SPS or clams.

When I add this kalk slurry, nothing closes up and nothing seems unhappy about it. In fact, I find the leather much more extend, but don't know if it had anyting to do with this.

Anyhow, if it wasn't for the hard sand, I probably would think there is nothing wrong.

Malhovoc, it is the Caribsea aragonite sand, not the oolitic sand. I don't know if that makes a diff. Anyhow, the tank has been up and running for over a year now so it is not brand new. So are you saying it will not break up/dissolve by itself if I stop the kalk?

Question: Does the 2 part systems cause this too?

[john rock]

IMO I think adding anything other than water changes to your setup is a waste of money and could lead to possible problems by adding it that way. I'm definatly not for adding KALK straight up! to a tank. I believe you could lead to ph spikes very fast and it only takes 1 ! bad spike to crash your tank!
I ran my 65g almost a year with just water changes. I might of try'd some additives here and there but that tank ran just fine.

[thien]

hmmm....good advice. I've stopped adding the kalk since I noticed the hard sand. Does anyone else have any thoughts?

Anyone know if the 2 part systems causes this to happen too?

[Flame*Angel]

I've been using this method for adding kalkwasser to my tanks for years without any problem of sand clumping. I have Anthony Calfo's book "Coral Propagation" and he states this method in his book also.

That said, adding kalkwasser to a tank that doesn't have critters using up the calcium and alkalinity can cause problems with ionic balance. I've been through this recently with my FOWLR tank. However, I really don't believe that it causes clumped sand. I was advised to use Reef Builder as a buffer for non-reef tanks.

This is a quote from Ron Shimek:

Rapid bacterial growth rates only occur without competition for space or nutrients. As the bacterial populations fill in all the open spaces growth slows and may stop altogether. Some bacteria also secrete a exterior covering called a glycocalyx. These are made of a hard sugar-like material similar in consistency to rock candy. Rapid bacterial growth may produce so enough of this material to glue sediments together. These sediment lumps may be glued so tightly together that hammering is needed to break them apart. In much reef literature, these lumps are said to be caused by calcium carbonate or calcium phosphate precipitation. Such mineral precipitation is rare; if a small sediment lump is placed in a weak solution of household chlorine bleach, it breaks down to the component sediment grains in a short time. If the lumps were formed from the calcium salts, they would not dissociate in the bleach.

Read the rest of his article and what to do about this here:
http://www.rshimek.com/reef/sediment.htm

[john rock]

good info FLAME, are you adding KALK in a slurry as well?? I heard it was very hard on pumps/powerheads as well as it would make for a cloudy tank.

[thien]

Thanks for the info Flameangel....so you've never noticed harden sand?
When you were adding kalk, how long would you take to pour it all in?

Are you guys saying I should stop using kalk?

[GaryK]

I was working in the tank the other day, and I also disovered a brick-like patch in the sand bed. I completely forgot about it until I read this post. I add Kalkwasser as a drip into the sump. I also add either Seachem Reef Builder or separate supplements depending on what needs adjusting. I've recently added some large calcium users, and I haven't yet managed to maintain the calcium levels at about 420 which is my target I vary between 380 and 420 ppm right now with alkalinity of about 3.1 meg. Do you think that these levels would have cause the sand to go hard like that?

Gary