Lighting through a glass top?

[fkshiu]

Old school reefers actually would want MORE evaporation - why? It allowed more the addition of more kalk. The need for kalk has lessened with the advent of Ca reactors and two-part dosing, but you should still take full advantage of your tank's ability to shed water. Kalk helps maintain Ca/Alk and keeps your pH up, plus it's dirt cheap in bulk (relatively speaking). Just get an ATO if you don't want to top up manually.

Anyway, glass tops cut down on PAR significantly. Just check out Sanjay's spectral plots of shielded vs unshielded MH bulbs.