Current Southdown-equivalent sand is...?

[Anonymous]

So it is wrong to say that aragonite differs from other calcium carbonate substrates?

No. The crystal structure is different.

How come sand beds of aragonite shrink over time?

Do they? I've always heard this but was never sure it was actually occurring. I guess it could be due to a localized low pH deep in the sand bed.

I'm basing all my questions on what I've read in Anthony Calfo/Bob Fenner's Reef invertebrates book, which claims that aragonite dissolves at a lower acidity because of it's structure and that it's the best choice for buffering as a result. It seems logical to me to suggest that two different substances can have the same chemical composition and behave differently because of the way they are formed (the old carbon/diamond argument), but I'm willing to be convinced otherwise.

 

[Anonymous]

It says it dissolves at lower acidity, or dissolves faster? What pH?

 

[Anonymous]

It says it dissolves at lower acidity, or dissolves faster? What pH?

It says that it dissolves at a range above 8.0, whereas standard calcite substrates will only start to dissolve at under 8.0 (I'm paraphrasing from memory).

 

[Anonymous]

It says it dissolves at lower acidity, or dissolves faster? What pH?

It says that it dissolves at a range above 8.0, whereas standard calcite substrates will only start to dissolve at under 8.0 (I'm paraphrasing from memory).

I looked at the book (page 33) and the quote is a bit confusing to me; specifically what "begin to" means in this context.

Aragonite will begin to dissolve, in fact, at a pH over 8.0...while calcite does not readily dissolve until a pH below 8.0.

From RHF's article here (note the levels of Ca and Alk where dissolution begins at typical aquarium pH):

W = 1 (risky: dissolution of aragonite begins here)

pH = 7.7
Calcium = 410 ppm
Alkalinity = 2.5 meq/L

pH = 8.2
Calcium = 340 ppm
Alkalinity = 1.0 meq/L

Sounds like incredibly low Ca and Alk in order to dissolve aragonite at a pH above 8.0.

 

[Anonymous]

Well, then, let me redirect the query in this direction :

It's a fish-only tank with some angels, butterflies, tangs, whatever.

What substrate is best?

Peace,

Chip

 

[Anonymous]

Well, then, let me redirect the query in this direction :

It's a fish-only tank with some angels, butterflies, tangs, whatever.

What substrate is best?

Peace,

Chip

The one you like the look of most.

 

[Anonymous]

Well, then, let me redirect the query in this direction :

It's a fish-only tank with some angels, butterflies, tangs, whatever.

What substrate is best?

Peace,

Chip

IMHO a very thin layer of stuff that's coarse enough to easily gravel vac, will stay put if you blow a current across it, and fine enough to look good. "Best" is going to be a matter of opinion, but keep in mind that (in a fish only) the sand is there for your visual benefit and nothing more (assuming you're not planning on adding some kind of burrowing/sand sifting gobies, wrasses, etc.), and can actually be an impediment to low maintenance husbandry. IOW it's really easy to suck detritus out of a bare bottom tank!

I like to blow a current across the bottom to keep detritus suspended so a fairly coarse sediment mix is what I like. I think something in the range of 1-2mm grains...

 

[Anonymous]

OK, if you're confused Matt, I've decided to agree with you and also be confused.

 

[Anonymous]

Thanks for the opinions guys...I'll just get a thin layer of coarse whatever. There aren't going to be any burrowing anything in there.

Harlequin tusks don't burrow, right? I don't remember them doing that, anyway...it's been a long time since I was into this stuff.

Peace,

Chip

 

[Anonymous]

Harlequin tusks don't burrow, right?

Nope.

 

[Anonymous]

Gee how about play sand with a few crushed oyster shells mixed in? Especially for a fish only tank.

 

[Anonymous]

Don't forget the ecoaqualizer