Rock tumbler

[Issue #6 rec.crafts.jewelry]

2) What would be a good grit to use?  (I built the tumbler so I
can remove the sharp edges off about 400 - 600 lbs of rocks that
I have in an aquarium. Average rock size is about 5 to 10 lbs,
and rock is red granite.  I don't want the rocks to look
polished, I want the rough look, but don't want them to pose a
threat to my fish - so only the sharp edges need be removed.  It
seems a waste to purchase and use the amount of course grit that
would be required for this amount of rock since I don't want to
go as far as would normally be the case when tumbling rocks.  Are
there any good choices for the grit other than the course grit
normally used in the first step of tumbling?

While I like to cut and polish rocks, I haven’t done any
tumbling, however, may I suggest that since you just want to
round the edges etc, just put the chunks in your tumbler with
some water and let it run slowly for a while. Sharp natural
edges should be rough grit enough for what you have in mind, and
as the tube fills with dust, the rocks will be protected a bit
from too much smoothing. You will get beach like rocks.

Must be one heck of an aquarium, convert your swimming pool?