This is great - I will go look for some :)

thank you!

Would having a glass top, but open sump(in stand w/open back) Limit the O2 transfer and keep heat in? When I upgraded my lights, I had my tank open for a week. Evap was crazy, 1g/day and thats only T5, not MH. I also noticed that the tank temp rose a few deg. Now, with a 5mm glass top, and the TEK 4 tube 24" light tank runs 80.8 in the day, no heater. Evap is less, bout 0.6g/day. I dont want to lose fish due to jumping, nor do I want to be filling RO every day

I use eggcrate in my sump to elevate "things"..... but would it soften or melt somewhat under the heat of the MH lights?

Hmm, in doing some testing with a sheet of eggcrate and my Tek light. The eggcrate takes away a little ligth and reduces what little shimmer I have to nothing. The glass top reduces about the same light as viewed through the side of the tank, but the shimmer is still there. Just testing the difference in tank heat with/without the glass cover right now.

i just recently took my glass off, it was standard 3mm, happy so far, but omggg evaporation is ridiculous without a top, i used to top up every few days now it's every single day 1/4'' gone, then again i did it for good gas exchange so thats the way it's staying, thinking of eggcrate though-

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.

do they really cut down on PAR that much? i remember one of the staff members mentioning that it barely lowered PAR by a few percent, and that some 95'ish% of light gets through, good to know though

Here are Sanjay's results for 150W DE HQI bulbs both with and without a 1/8" glass shield:

http://www.reeflightinginfo.arvixe.c...&Submit=Submit

The glass causes a good 20% loss of PPFD (a.k.a. PAR) for nearly all bulbs.

thanks for the link, 19% up for me! unreal it was thin glass too, 3mm

and that's WITHOUT 1/8" salt creep built up on the glass to boot. you'll lose a lot of light so it's a major tradeoff you'd have to consider if running a glass top.

using egg crate on halides is a bit of a pain with most reflectors because it'll block a lotta light on the outer edges. egg crate's really only best for flourescent lighting. maybe look into an auto-top off unit? i love mine.

a good ol' canopy works wonders for keeping fish in :)