Well... The 50W bulb ended up creating so much heat that it cracked the top glass - not in a disaster kind of way so I'll live I went out and bought a energy saving spot bulb of 11W which equals 50W's in terms of the light amount it produces. This is working really well (not cracking the glass) but I'll need one or two more to get sufficient light at the bottom. So now my qustion goes:
Which kind of light is it that results in leaf sunburn?? UV, visible or IR/heat??

If it's the visible/white light I'll be in trouble since this will be very high in top, but if it's any of the two others I think I'll be ok by putting catts. and dends. at the top.

What do you guys think??

Christian