i've seen larger glass pieces (10-15lb) used before with great results it all depends on ur tastes really. i doubt the glass would really have any adverse effects. but if u'r worried put it in a smaller tank for a few days, test the water, and see what happens. good luck to ya.
oh and Dr. Joe, that's definitely a chrismas story. ( it must be french)
oh and Dr. Joe, that's definitely a chrismas story. ( it must be french)