Short light, long tank?

[debbie g]

Does anyone see any probs with putting a 5 ft long mh light over a 6 ft long tank? I just thought it would be that much cheaper for the 5 ft lights. And that there would only be six inches on each side of the tank that is not directly under the light.
Also, What is the difference between a "MH Power compact fixture" and a fixture that doesn't say "compact"? They are physically the same size, as in both say "60 inches" or "72 inches" Is one better than the other?
I just read in one of these threads that you shouldn't put your MH lights above the glass/plexiglas of your tank because you will be blocking the UV from your sea critters. Is this true? Cause I'd have to rethink EVERYTHING. I wanted to do a reef tank with mostly jawfish, gobies, firefish (All major jumpers) so I was happy that I have the very secure fitting glass/plexiglass lid. But if it IS going to block out the UV, I won't be able to have any eventual corals? I'm so confused.
Also, the water pumps, I see a lot of you mention MAG.
I found a Mag Drive Pump, it was considerably less money than say a Little Giant or Iwaki, Is Mag Drive Pump the one that a lot of you are swearing by? Is it used for your main system pump or only for powerheads?
I'd appreciate any help I can get. Thanks

 

[debbie g]

Ugh, I guess this is what I get for posting a four-part question.
I'll try to figure it out I guess.

 

[nacl-man]

MH Power Compact? That would say to me that it is a fixture with a mixture of both MH and PC bulbs. Different types of bulbs that are typically mixed together. I've never seen a 5 foot long MH bulb, although that would be pretty cool.
A MH fixture is going to need to be far above the water to avoid any spray hitting the bulb and cracking it, I've always thought it necessary to put some sort of barrier between the bulb and the water. However I'm afraid I can't help you there as I don't know. I would think not, as long as you kept it clean of salt creep and water spots.... but again I dunno.
Mag drive pumps are excellent, I have used them before without issue.

 

[flydan]

Hey,
Well I'll take a stab at this one and then I'm sure someone else will chime in too.
I don't see a problem with the shorter lights. I'd just build my reef up in the middle and leave the sides open. You'll get better water circulation that way. Also, you could put low light corals there, such as mushrooms.
The MH power compact system sounds like one that has MH fittings and pc fittings for blue actinic lighting. (you'll want both anyway.)
Most people would suggest that you don't cover your tank for a couple of reasons. One is that it gets salt splash on it and reduces the amount of light that gets through to your tank. The other reason is for better airation of your water. Also, if you put lights right on top of a glass top you will have heating issues to deal with. If you have jumpers or escape specialists you can put a canopy on your tank. These are usually 10 or 12 inches high if store bought, or what ever you want if you DIY.
Can't help you with the pumps. Sorry.
HTH,
Dan'l

 

[flydan]

See! In the five minutes it took me type an answer you got another reply.
:joy: :joy:

 

[debbie g]

Yay! Thank you both so much for responding. Its amazing how much you THINK you know and then find out...well...you don't. I will just be as humble as possible, keep reading the books, keep reading the posts, and hopefully I'll have some degree of success. Thanks again!