There are a few of us on here that continuously repeat ourselves on the danger of feeding FW (goldfish, guppies, mollies) to marine livestock.
It is a very important issue towards the long term well being to the animals you keep.
This link is a very good article on the subject written by Ph.D. Rob Toonen.
Section 2 covers live feeders.
The only portion I disagree with is where he mentions hand feeding. Use a feeding stick or other artificial feeding apparatus.
http://www.advancedaquarist.com/issu...003/invert.htm
Enjoy,
Ed