Lighting alignment

[Big Country]

Maybe a stupid question but figure I'll ask. Never thought of it before. Thought about it because I had T5's before and they ran end to end on my 75.

 

I have a standard 180g tank 6x2x2 with 3 250w MH's in Lumenmax Elite reflectors, first time I've ever had MH's. Does it make a difference which way the bulbs face? Or do the reflectors reflect the light the same way no matter which way the bulb is facing? Currently all 3 of my reflectors are hanging with the base of the bulb toward the rear of the tank so the bulbs are running front to back. I would imagine it might make a difference on my center light because it's a Oceanic tank with the wide glass center brace but just don't know.

[Coral Hind]

That is how I would put them. The shape of the reflector spreads the light out fairly well but there is still a little less PAR on the side of the reflector where the bulb base is located. Since the base is near the back of the tank where the rock work and corals are normally higher this slightly lower PAR level is fine. Your placement then allows the stronger PAR to be at the front where corals normally end up being placed lower.

[Ryan S]

With some bulbs, I believe, they have to be turned a certain way though in the socket, is that correct?

[onux20]

With some bulbs, I believe, they have to be turned a certain way though in the socket, is that correct?

I thought that was just with DE HQI bulbs. The "nipple" needs to face up.

[Ryan S]

I thought that was just with DE HQI bulbs. The "nipple" needs to face up.

 

ah, okay. i wasnt sure if it was just DE HQI or some mogul bulbs too.

[Coral Hind]

The nipple effect applies to all MH bulbs, not just the DE. The nipple or exhaust port you see is from when the arc tube was made. There has been a lot of debate on reef boards over the years as to where it should go, up or down, or does it even matter. I gave up trying to correct people on the issue.

 

The nipple should always go up if possible or to the sides, just not down. The reason is the center of the arc will always rise slightly from convection. If the nipple is up the thicker glass is heated and helps to maintain an even temperature of the arc tube's surface. If the nipple is down the arc will heat the thinner glass to a higher temp then the thicker glass nipple at the bottom. This inconsistant temperature of the arc tube will allow the salts / metals to collect in the cooler, down facing nipple, and not allow it to enter the arc stream. That can cause a flicker, change in intensity, or shifts in the spectrum. When the thinner glass is on top it can also start to buldge and lead to an arc tube failure.

[Big Country]

I don't have HQI bulbs on my tank, am running standard Radium 20K 250w Mogul Socket bulbs.

[DaveS]

The nipple should always go up if possible or to the sides, just not down. The reason is the center of the arc will always rise slightly from convection. If the nipple is up the thicker glass is heated and helps to maintain an even temperature of the arc tube's surface. If the nipple is down the arc will heat the thinner glass to a higher temp then the thicker glass nipple at the bottom. This inconsistant temperature of the arc tube will allow the salts / metals to collect in the cooler, down facing nipple, and not allow it to enter the arc stream. That can cause a flicker, change in intensity, or shifts in the spectrum. When the thinner glass is on top it can also start to buldge and lead to an arc tube failure.

 

Wow that is one highly technical explanation! I just kept the nipple up cause I figured the light shining through the nipple would be slightly dimmer (distortion, thicker, etc.) so I didn't want it down and reducing the light going into the tank (however slightly).