For those who may want to try mossballs in they're goldie tanks.
You can propogate the moss balls simply by tearing a small peice of the original ball and roll the new small piece into another ball.
Use the new small peice and see if the goldies eat it.
General rule of thumb is that the darker the green color the less likely a goldie will eat it, however that is based upon the fact that the darker the green usually the harder the leaf and goldies prefer softer leafed plants over crunchy ones.
On a side note, I have java moss, red tiger lotus, dwarf sagitarius, water sprite, hornwort, and pennywort in my goldie tank, all of which some goldies will eat. however, none of my goldies seem interested in....yet...they've been in there for approx 6 months though so I'm pretty sure they dont like it.
I also have java fern, bolbitus and anubius which of course they dont even look at.
I just bought a moss ball myself last week for $9.99 (Canadian dollars).