Aragonite? Coral Sand?

[Fatty]

I've been looking at getting some aragonite for a top layer substrate in a plenum type system..

I understand that Aragonite is a polymorph!? (different) of Calcite (which must be the most common form of calcium carbonate).

If Coral sand is lots of dead coral, and corals create aragonite skeletons then surely coral sand is in effect aragonite sand but just alot cheaper???

I've read that sometimes due to the condition of the sea corals produce a calcite skeleton, but I'm assuming the majority form an aragonite skeleton.

I'm not a chemist so does anyone know if there is a difference,

I've got my eye on a big bag of 2-4mm coral sand, which I'd think ishud be mostly aragonite (if coral skeletons are).

I'm thinking there may be a flaw in my thinking, or everyone would be saving a load of money just buying coral sand...

 

[1entra]

I dont know all the scientifics behind it but I'm currently using a mixture of Live sand and coral sand in my tank and it all seems to be doing quite well!

 

[Lynden]

Both should work.

 

[Fatty]

Both should work.

Thanks for the comments,

So is it generally thought that coral sand is infact made up of aragonite rather than calcite??, as aragonite is preffered I understand.

It's confusing as coral sand is about £18 for 25Kg and Aragonite sand (Caribsea stuff) is about twice that at £50 for 25kg at least..

What do you get with the caribsea stuff that you don't in coral sand??

Thanks

 

[Donya]

Only downside to coral substrates is that the diameter is often larger (at least in the bags I've seen), which can result in debris buildup if you don't have a lot of substrate-dwellers to turn it over. I've not really had that problem myself, but I know some people complain about it.

 

[Fatty]

I've managed to find what I think is the reason for aragonite sand or gravel being so expensive in comparison to coral sand..

Coral sand altho composed partly of coral (aragonite) also has alot of tiny or larger broken marine shells from snails etc., and the composition of a snail shell or similar mollusks is calcite rather than aragonite, so it's a mixture which would be suitable for the first layer in a plenum (e.g. would not solidify like pure aragonite).

So the expense from buying purely aragonite I'm guessing is somehow they seperate out the non aragonite components such as shells and rock etc, and this process is why you pay more for aragonite!?

So I reckon by buying large size 2-4mm of coral sand it will pretty much be all coral skeleton(seems to be the case from inspection), therefore a cheap source of aragonite.

Which I can then use as the top layer of my plenum with of course some substrate sifters to keep it clean..