[Dive_Master]

I just installed two (2) 250 Watt Ushio 10,000k MH lights 9 inches above the water level with no glass tops.

The tank is 20 inches deep and 48 inches long. I kept the lights away from the glass support in the middle of the tank, so there is some shade in the middle of the tank.

I can live with that, but the tank appears to be less bright than it was with 300 watts of PC lights (actinic and 10,000k).

Everything that I read says that the 250W Bulbs are plenty , but the tank is not that bright. Are the 2 250 W MH enough for my tank?

I want to put some SPS in there. If so, How low below the water level or better yet below the light should I place them?

Thanks,

[Jimbob]

2X - 250 watt MH is plenty... as far as them appearing dim, I must ask a very silly question, but one that needs to be asked... you are using a reflector with them correct? If so, what kind of reflector? Perpendicular orf horizontal design, or are you using a pendant of some kind? Also, are the bulbs new, or did you get them used from someone?

It is not uncommon for the MH to "seem" a little less bright with the naked eye... this is due to the refraction of the light source within the water column and the resulting shimmer lines, etc. PC fluorescent lighting always "appears" much brighter than it really is.

As for the acros under your 250 watt lights, all acros should be great in the top half of the water and most species could easily be kept in the bottom half (based upon your stated 20" depth).

Give yourself some time to adjust, make sure you are using a high-quality reflector (as opposed to a flat piece of sheet metal), and replace the bulbs if they are older used ones (if older than 9 months, replace them to be on the cautious side).

More importantly... ENJOY!

[Dive_Master]

Originally Posted by Jimbob

2X - 250 watt MH is plenty... as far as them appearing dim, I must ask a very silly question, but one that needs to be asked... you are using a reflector with them correct? If so, what kind of reflector? Perpendicular orf horizontal design, or are you using a pendant of some kind? Also, are the bulbs new, or did you get them used from someone?

It is not uncommon for the MH to "seem" a little less bright with the naked eye... this is due to the refraction of the light source within the water column and the resulting shimmer lines, etc. PC fluorescent lighting always "appears" much brighter than it really is.

As for the acros under your 250 watt lights, all acros should be great in the top half of the water and most species could easily be kept in the bottom half (based upon your stated 20" depth).

Give yourself some time to adjust, make sure you are using a high-quality reflector (as opposed to a flat piece of sheet metal), and replace the bulbs if they are older used ones (if older than 9 months, replace them to be on the cautious side).

More importantly... ENJOY!

tHANKS,

i AM USING SPIDER TYPE (high polished) REFLECTOR. as INSTRUCTED BY THE manufacturer, I installed these perpendicular to the front of the tank.

[kevinpo]

Are they mogul mount or double ended bulbs? If mogul mount be sure the nipples on the inner envelope of the bulb are pointed up when you screw the bulb in.

HTH,
Kevin

[Dive_Master]

Originally Posted by kevinpo

Are they mogul mount or double ended bulbs? If mogul mount be sure the nipples on the inner envelope of the bulb are pointed up when you screw the bulb in.

HTH,
Kevin

Thanks, but why is that important? They are pointing down after I screwed them in.

[kevinpo]

I thought they might be

"When pointed down, the nipple tends to collect condensed halides when the lamp cools down. These halides tend to not vaporize as easily down in the pocket of the nipple when the lamp is reignited, so the nipple tends to darken prematurely from the collected halides. This cuts down on the light output somewhat, but more importantly, the darkened nipple heats up more than the surrounding bulb since it begins to absorb light energy. This localized heating tends to result in degradation of the quartz envelope over time called devitrification. Since the nipple is already the weakest point of the bulb this can result in the bulb rupturing."

The above quote is from Ken who does testing of metal halide bulbs for a living.


To get them to tighten at a different position turn off the power and wait till they cool then reach down into the bottom of the socket. There should be a small tab where the end of the bulb makes contact. Gently pull this up so that when you screw the bulb in, it contacts sooner. You will be surprised at the result.

Halide bulbs also need 80 -100 hours of burn in time to reach their final color and brightness.

Regards,
Kevin
PS: Here is a link to an article you might find interesting. Note the section titled Bulb orientation:

http://www.advancedaquarist.com/issu...03/feature.htm

[Dive_Master]

Originally Posted by kevinpo

I thought they might be

"When pointed down, the nipple tends to collect condensed halides when the lamp cools down. These halides tend to not vaporize as easily down in the pocket of the nipple when the lamp is reignited, so the nipple tends to darken prematurely from the collected halides. This cuts down on the light output somewhat, but more importantly, the darkened nipple heats up more than the surrounding bulb since it begins to absorb light energy. This localized heating tends to result in degradation of the quartz envelope over time called devitrification. Since the nipple is already the weakest point of the bulb this can result in the bulb rupturing."

The above quote is from Ken who does testing of metal halide bulbs for a living.


To get them to tighten at a different position turn off the power and wait till they cool then reach down into the bottom of the socket. There should be a small tab where the end of the bulb makes contact. Gently pull this up so that when you screw the bulb in, it contacts sooner. You will be surprised at the result.

Halide bulbs also need 80 -100 hours of burn in time to reach their final color and brightness.

Regards,
Kevin
PS: Here is a link to an article you might find interesting. Note the section titled Bulb orientation:

http://www.advancedaquarist.com/issu...03/feature.htm

Thanks for your info and the article I found helpful.

I changed the mogul socket around so now the nipple is pointing up. I already see the difference (small but noticeble).

Thanks for your help.