Well, I got 2 marimo moss balls just for my Rain, a tennis-sized one and a slightly smaller (but still considered a giant one). They cost me quite a bit, but I thought that it was worth it if my fish is happy.
So far my Rain's been playing around with the other decorations (floating plastic plant, terracotta pot, heck even the thermometer!

) but he's ignored the moss balls completely. Although he did stare at one for the longest time and then swam away.
I told my friend about it, and his reply was "just talk to him sternly" like Rain was a little kid to be disciplined and it made me laugh
Do your bettas like their moss balls?