quartz and most plastics are transparent to UV. Ingrid

If so then the tube is very cheap. Tap Plastics has 1" dia x 1/16" wall
six foot long tubes for $4.30

In good units, the most costly part is the quartz sleeve, about 2x the
light.

See above. A brief web search finds a 40w UV bulb for $50. A little
PVC and epoxy, and a ballast from the DH's desk lamp and off you go...

The same site (pondbiz, just the first one I found) has an assembled 40w UV for
$253

Good point. As I recall, the Koi USA one used a plexiglas tube. Dunno if
thats cheaper or not, or how transparent to UV it is...