UGF/heater method

> Place a UGF plate in the bottom of the tank.  If you are using a fine 
substrate that might fall through the >plate, wrap it in fiberglass 
screening first. (I use monofilament fishing line to.......
>difference between this system and a standard UGF. Instead of placing 
airstones or power heads in the
>risers, drop a 7.5W submersible non-thermostatic down each one. (I use 2 in 
a 55G tank)

Thanks, Karen for replying to my question.  I've got a few more questions on 
the method. Is the 7.5 W heater in contact with the bottom of the aquarium - 
doesn't there need to be water freely flowing around the heater - any chance 
of cracking the glass?  Also, I've seen fiberglass screening in hardware 
stores, used for window screening.  Is there  fiberglass screening with a 
smaller mesh size........where is this sold?  I have seen a fiberglass cloth 
in automotive stores, but I would think this would become clogged over time. 
 Would nylon netting be an acceptable alternative?