Basic questions on metal halides

[kiwiandman]

I have a a narrow hex tank that only allows for a 20" max light. I have a glass top on the tank, can a pendant light be set directly on the glass? Do they get as hot as other halides, would it make the tank too hot? I know they make clamp on lights but I don't have room because of a hang on skimmer.
Keeping the top off is not an option, I have jumpers. I accidently left the lid up last week and a goby commited suicide.
Also, does condensation and salt buildup under the glass inhibit the light in any way?

 

[chipmaker]

Not a good idea to place any light directly on top of another glass top especially a MH light.
They make a grid used i suspended ceilings called egg crate. Its a white or yu can get it in black or chrome as well 1/2" sq grid material that works great at keeping in jumpers and solves the problem of not being able to have a open top tank. Its cheap less than $10 for a 2 x 4 foot piece which is esay to cut with a pair or scissors or wire cutting pliers. Yiu will get high heat retention, and lots osalt creep with a full glass cover. Open top aids in gasseous exchange as well. Yes, dried salt or condensation or even bare clean glass all play a part in reducing light transmission. YOu may get by with MH lights on an open top tank without a fan but I sort of doubt yu can be so lucky on one with a totlaly enclosed glass top without fans or a chiller.