limpets good or bad

"robin gordon" writes:

just before going to bed I switched on a light to check the tank and
discovered hundreds of small limpet like creatures (2-5 mm in dia.)
all over the live rock. are these a good sign or bad. what is
recommended if they're bad, how do I exterminate so many without
destroying my setup. during the day they are hidden in the
rockwork.

Unless you observe damage that you can actually blame on them, they're
almost certainly beneficial to your tank. They will generally be eating
"slime" a.k.a. cyano, monocellular algae, other bacteria films, etc.

When diatom and cyano blooms "go away", as they eventually do, it's
usually populations of this kind of creature that are doing the
cleanup for you.

Regards,
Ross

-- Ross Bagley http://rossbagley.com/rba
"Security is mostly a superstition. It does not exist in nature...
Life is either a daring adventure or nothing." -- Helen Keller