400w MH question single vs double.

[t.priscu]

Hi Guys,
Are single ended 400w lights different than double ended 400w as far as PAR or something? The reason I ask is that I picked up a used 400w fixture to cover 1/2 of my frag tank. I already have one single ended 400w MH hanging and all frags under it are doing great. When i hung up the double ended 400w MH at the other end. Just to test everything would be okay i stuck a frag of sps under it. In an hour it had bleached out. I kept raising it up to as high as it would go. Still bad results, so as a final test i screwed it directly into the ceiling to see what would happen (i do not plan on keeping it like that). Anyways It still bleached out corals. Bulbs are both new, however single halide bulb is a 20k vs double ended is a 14k. I can shade under the double ended fixture but im just curious why i should have to. It's so high already.
Anyone have an idea on what the deal is, why does the 400w double cook everything but the 400w single does not and its even lower?

Lights over frag tank

400w ballast for the double ended MH

 

[BrentH]

That seems crazy with it that far up? How deep is the frag tank

 

[power boat jim]

Do you have a glass shield on the double ended fixture?

 

[hillscp]

De bulbs don't have uv shields. Does the fixture have a glass uv shield?

 

[t.priscu]

There is no glass shield, so that could be it?! That would be awesome bc this has been stumping me like crazy!

 

[Peter Eichler]

That's the problem... Also, 400w MH seems like bigtime overkill on asuch a shallow frag tank.

 

[t.priscu]

Yeah it is but i bought it bc a fellow local reefer was dumpin it cheap. So just any cut glass from lowes or somethjng will solve the problem or do i need something special?
Thanks again for all the help guys

 

[Michigan Mike]

What ballasts are running on what bulbs?
Your double ended bulb/pendant looks very high. Obviously you need a UV glass shield on it, the single ended bulbs have a uv shielded envelope (or bulb) but more info is needed.
What corals do you have under each bulb/ballast combo.

It looks to me that your 400w double ended bulb that is extremely high up is not what you say it is and isn't close enough to give your coral enough light.
Lack of light will make corals appear pale & in one cases itch SPS brown before it gets pale & dies. There is a big difference between pale & bleached.

I can tell from looking that double ended bulb isn't what you think, something is not right.
Looks like a 150w double ended bulb that is wayyyyy to high above the tank.

What ballasts are on each and what bulbs are in each?....this will be a good start, ya?

 

[t.priscu]

It is a 400w bulb and as far as im told a 400w ballast. Its so high because on my first test the coral bleached so i raised it , another test gave same results, so just to test the max i hooked it to the ceiling. I wasnt aware of the UV issue so now i need to get some glass for the pendant but not sure what to ask for . It isnt that the corals look pale the test frags of sps turn practically white. Once i move them back to the other side of the frag tank they are def bleached from the short time under the double ended fixture. Once i have the glass shield ill do another test with it at the ceiling and if all stays well ill lower it to the correct height.
Thanks again for the help

 

[Peter Eichler]

Yeah it is but i bought it bc a fellow local reefer was dumpin it cheap. So just any cut glass from lowes or somethjng will solve the problem or do i need something special?
Thanks again for all the help guys

Any glass will work and will shield out nearly all the UV.

 

[t.priscu]

Outstanding. Thanks for the help !

 

[Michigan Mike]

The lumenbright pendant is putting a ton of light on the wall but it is a spotlight impaired to the reef optix style pendant which should be spreading the light on the wall also but it looks very dim in comparison. It doesn't look like a 400w to me, from looking at the pics.

You can order the glass if you know pendant it is, or cut some glass @ the hardware store but it nev seems to turn out as good IMO.