I vote "benefit." Snails are the best at keeping algae under control. I've
never had a problem with pond snails eating my plants. But they are hell on
algae.

If you read the archives of the this group, you'll find that many a hobbyist
has introduced loaches to get rid of snails, then found themselves with an
algae problem instead.

Some people find snails unsightly, but I don't. I consider them a natural part
of the ecosystem. Of course, you don't want your tank overrun with thousands
of them...but as long as your tank is in balance and you're not overfeeding,
the snail population will stay in check.

The only drawback to pond snails is that they can get into the filter and, in
some instances, damage the impeller. Or at least make a racket, rattling
around in the impeller chamber. I use a foam prefilter on my filter intake to
keep the snails (and the baby fish and shrimp) out.


Leigh

http://www.fortunecity.com/lavender/halloween/881/