Be careful about using values for the "weight of sand" that may be
derived from inorganic sand -- the sort usually used to mix concrete.
That rock is a lot denser than the calcified coral heads those parrot
fish are chomping on (which are actually quite porous, especially at
the surface).  If you have any dead coral samples around, try this:

1. weigh your sample.
2. use Archimedes' old trick & submerge your sample in a beaker of
water & see how much volume it displaces.
3. divide weight by volume and use that multiplier on your 500 kg/yr
to get the parrotfish production output.

MUCH more accurate than using some figure of unknown provenance!

----------------------------------------
Steven Allison-Bunnell
Principal, Natureboy Media
533 Blaine, Missoula, MT 59801
(406) 542-8281  fax 728-8708
[log in to unmask]
http://natureboymedia.com
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