The Ultimate DIY Rocks!

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These expanding crystals you speak of sound like silica gel. If so, it is a desiccant that will draw moisture out of the concrete and introduce silicates into your water. You will have diatom issues if you use that stuff.

How do you get rid of the silica gel crystals before you put the rock in the tank?

Just to clarify for some, there are no chemical benefits to using salt to create void space. It's just a reef safe additive that dissolves readily. Sugar would work better, as it wouldn't interfere with the chemical reaction of the hydraulic curing process, but it's a little more expensive, and hard to get in large crystals (cane sugar/rock candy).

There are lots of polymer modified (quick curing) cement mixes out there that are not water-proof, and have the same pore matrix as regular portland. I have used one by Bomix that worked well. It had a longer work time (20 minutes vs. 2 minutes), so it was easier to use than the King or Quikrete brands.

You can also use calcium chloride-based additives to speed the setting time by 25%.
 
<a href=showthread.php?s=&postid=10183498#post10183498 target=_blank>Originally posted</a> by mr.wilson
These expanding crystals you speak of sound like silica gel.
Click to expand...

Silica gel and the Polymer Cyrstals I am talking about are two different compounds.

Silica gel is Sodium silicate, Na4SiO4.
Polymer crystal is Polyacrylamide an acrylate polymer, H2CHCONH2.

The Polymer Crystal is a type of plastic.

It can be removed from the concrete with a saltwater bath outside of the tank.

If anyone tries using these before I post my results, soak the crystals in water before you add them to your concrete mix. That way they don't expand in the setting concrete and don't steal the water from the mixture.
 
<a href=showthread.php?s=&postid=10182997#post10182997 target=_blank>Originally posted</a> by sunkool
All this coming from someone who posted this
Click to expand...
Sunkool, this is an example of a personal attack.

If you responded with, "I disagree, salt is great for the following reasons..." is not a personal attack and adds credence to your argument.
 
Guys...I have been following this thread for a while now. It's great to debate the pros and cons of various ingredients and techniques.....but it really takes away from the development and sharing of ideas when the conversation breaks down to this level of exchange. Let's get back on track please...
 
I have these crystals for the garden and plant pots. Really cool stuff! How does a saltwater bath remove them from inside the rock...does the saltwater break them down where freshwater does not?

Or does it need to be removed? They are just filled with water anyway....

Here is what I am referring to:

http://www.watercrystals.com/How_water_crystals_work.htm



<a href=showthread.php?s=&postid=10184200#post10184200 target=_blank>Originally posted</a> by michaelalan
Silica gel and the Polymer Cyrstals I am talking about are two different compounds.

Silica gel is Sodium silicate, Na4SiO4.
Polymer crystal is Polyacrylamide an acrylate polymer, H2CHCONH2.

The Polymer Crystal is a type of plastic.

It can be removed from the concrete with a saltwater bath outside of the tank.

If anyone tries using these before I post my results, soak the crystals in water before you add them to your concrete mix. That way they don't expand in the setting concrete and don't steal the water from the mixture.
Click to expand...
 
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I've used those polymer crystals before, but I just assumed it was silica gel.

The question remains, how do you remove it, as it's a regenerable media?
 
Any reason why they would need to be removed from inside the rock? They can be brushed off the surface very easily I would assume...for aesthetics
 
<a href=showthread.php?s=&postid=10184486#post10184486 target=_blank>Originally posted</a> by mr.wilson
The question remains, how do you remove it, as it's a regenerable media?
Click to expand...

Supposedly a saltwater bath will dissolve the crystals.

I will let you know how that works out on Sunday after testing it.
 
<a href=showthread.php?s=&postid=10184520#post10184520 target=_blank>Originally posted</a> by michaelalan
Supposedly a saltwater bath will dissolve the crystals.

I will let you know how that works out on Sunday after testing it.
Click to expand...

I can try this tonight.....I will post what I see.

Anyone have thoughts on the perlite question I posted?
 
Perlite is a volcanic rock that has a lot of water content - it expands when heated. I'm not seeing any reason it couldn't be used, but also can't see any reason to use it either. The purpose isn't to make light-weight rock, but porous rock...
 
<a href=showthread.php?s=&postid=10184486#post10184486 target=_blank>Originally posted</a> by mr.wilson
I've used those polymer crystals before, but I just assumed it was silica gel.

The question remains, how do you remove it, as it's a regenerable media?
Click to expand...

I think you and I might be thinking of the same stuff, Mr Wilson, the stuff I have used for flowers is not something I'd want to add to my rock.
It sounds like this stuff might be different, but still, as difficult as it can be to remove stuff from the rock (pasta and fish food come to mind), I think I will pass on this one :)
 
Why does it need to be removed? It doesn't rot or breakdown...it would accomplish the same thing as salt...ie pockets of water inside the rock.
I don't care what gets used as long as it works....just bouncing around ideas here.

As far as perlite is concerned it is porous and has tons of little voids....more surface area for bacteria to breakdown nitrates perhaps? Being light was not the main reason for consideration but a pleasant bonus. It would act as a very cheap aggregate and filler, method to create pores in the rock, its white, light, and inert. All of these are good reasons to use it I think.
 
<a href=showthread.php?s=&postid=10184670#post10184670 target=_blank>Originally posted</a> by Neptune777
Why does it need to be removed? It doesn't rot or breakdown...it would accomplish the same thing as salt...ie pockets of water inside the rock.
Click to expand...

Those crystals, from the sound of it are going to start breaking down when they encounter salt water. Now going on what I know of the crystals I used, these are going to be sort of rubbery, now imagine that breaking down. I picture slime - sort of like what was on Nickelodeon when I was a kid.

Voids help water move through the rock - if the voids contain stuff, they aren't really voids...

Your points on Perlite are taken - I haven't been up very long and didn't completely think that through, but I will just say that perhaps a few tests or more research should be done, especially in respect to absorption - will perlite absorb and hold things like phosphates, ammonia, nitrates/nitrites, or anything else detrimental to the tank? I'd think a quick email to a manufacturer would provide that info...
 
As far as absorbtion is concerned I would be suprised if it did this sort thing...at least if it did this more than the cement, and sand or crushed coral additives. It is basically glass with lots of air pockets I believe. Its main use is to aerate and to keep soil from compacting.
 
Neptune

I think perlite has a low alk level which may allow you to increase the amount of calcium you add to your tank.

According to wikipedia, “Ionic substances like salt cause polyacrylamide to release its absorbed substance.”

It's used in contact lenses and in plastic surgery so I imagine it's safe enough.

Insane is right, it might become a gel and leak out of the rock. I imagine the skimmer would have a field day with that.
 
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