Removing glass cover from your tank would be a good idea just for proper gas exchange; someone just lost all the fish not too long ago on here (Alfredshouse?) because of lack of O2. Our tanks are not perfectly designed for proper gas exchange anyway.
Ideally tank height needs to be equal to its width, or greater like a lake or an ocean, but this is the case only with cubes, so we all need some help with gas exchange.

Re T5, I don’t use any cover and my 6 lamps Tek fixture is on the legs at the lowest setting which is about 6” or lower from water surface just above the splash level

Does it effect Temp in your tank?

Didn't notice a temp difference in my tank

The problem with removing the glass cover is that you're going to expose your T5 reflectors to salt spray and humidity which will lead to pitting of the reflectors and eventually diminish light output.

Then the other problem you have is that if you choose to protect the reflectors by putting the acrylic shield on the fixture you're going to trap heat in the fixture around the lamps causing them to burn out faster and lower the PAR produced. Ideal T5 output occurs when the cold spot on the lamp (the end where the label is on the lamp) is kept at a temperature around 115-120 F. And this is not simply accomplished by blasting the lamps with a fan because the air should be directed at the cold spot on the lamp. The concern regarding overheating the lamp when leaving the acrylic shield in place is negated when you have a fixture with active cooling. And again, this is why it is prudent to purchase a quality T5 fixture - you save on lamp replacement costs in the long run and you get better output.

One of the trends I've noticed in this thread is that the majority of posters are relatively new to the hobby. I think what unfortunately happens is that new hobbyists read that T5s are great and see people keeping higher demanding corals with them. So they've done part of the research when it comes to making a lighting decision but they unfortunately miss part of the story - the important part where lower quality fixtures produce significantly less light output and the importance of things like high quality individual reflectors, active cooling over the cold spot, and appropriate lamp shielding among other factors such as quality of ballasts.

Hey, I had all these questions I was going to ask you when you came by.
I have my reef at 80F. I will watch it closely, how far is your light above the water level.
Do you have the acrylic cover on yours?
Thank-you, Banditpowdercoat,
This is fun right!?#*

No wonder so many give up, just when I thought I had an answer........My light is crap
make that both are. When I stop crying I will hit post quick reply, nope i will jump the gun.

Ya Leah, I'm second guessing my choice in light fixture now too. Well, originally I never wanted to keep SPS. Now I have a Clam, and am thinking maybe a birdsnest woult look good there, a Acro there........ I keep my yank at 77-78. heater comes on in winter, but never in summer. I have a A/C unit in the living room that helps. I will be needing a larger A/C unit when I get the new tank tho.

So, I'm thinking, I need 4 new bulbs now, and the TEK light isnt active cooled. I may just try a 250W MH light from www.fishneedit.com I know they are not best quality, but for the price, I can sure try. I have allways loved the MH shimmer.

Leah,

The Tek light isn't crap per se. It's just that a lot of hobbyists seem to see the recommendations regarding using T5s and then go out and buy something like the Tek fixture thinking they're getting a good T5 fixture. Unfortunately, they're missing most of the critical design components of a good T5 fixture. And as I've stated previously the initial savings of buying a cheaper Tek are eventually obliterated when your lamp replacement is sped up, and your output is diminished so you have to run more lamps to achieve the same output produced by a higher quality fixture.

With that said, I ran a Tek light temporarily on my SPS dedicated tank for about 7 months and it kept things alive but they certainly grew slower. Something like a Tek light would be fine for a soft coral or LPS tank and obviously will work with SPS - it's just not even close to the best option for an SPS tank. And users need to understand that while they're "using T5s" there's a HUGE difference when you're comparing output and efficiency from fixture to fixture.

The most cost effective lighting solution is still MH in my opinion. The up front costs and lamp replacement costs on a quality T5 fixture make them a nice toy with which you can more readily manipulate color. However, there are other down sides to T5s for lighting an SPS tank such as the dreaded pastel coloration or "chick corals" (Brad loves this look).

I get it. I like what I have in my reef, I am not interested in getting to complicated with
the more light demanding creature's. Love this reference to chick corals thats good I guess that is me too! Thank-you, I can finally expel that breath I took over an hour ago.
Thank-you again Canadian,
Leah

I love the info on Tek's vs higher end models.

I like my Tek and have a great track run with it. I really would like to see some more technical comparisons on the different fixtuers, much like the Sanjay MH bulb tests before I am convinced however.