Distance from water and light

[CoMMaNdeR]

Today I placed the new canopy on top of my 180g tank. Light connected there are 3 metal halides of 150W each and 4 PC's of 30W each.

The distance from the lights and the surface of water is about 14 inches. Is this good or alot guys? What distance usually you make between lights and the water surface please?

Thanks.

 

[SlowCobra]

Being that you only have 150's on a 180. I personally would move them down a few inches. I am assuming by 14 inches you mean the actual bulb height from the water. I would move it down to probably around 10 on the actual bulb height. As is stands depending on how deep the sandbed is the light will need to punch through roughly 34 inches to reach the bottom. Thats a long way for a 150.

 

[CoMMaNdeR]

My tank is 30" deep and the lights are about 14" far from the surface of the water. Should I make them about 10" or they are good like they are?

 

[SlowCobra]

Must be a 4ft 180. Honestly I think the 150's are way too small for that high of a tank. At least for keeping SPS in anything but the top 1/3 of the tank. The closer to the water you make the bulbs the less the light is going to spread. At 10" light bulb height your sand bed will be approximately 3 ft from the bulb. In my opinion the par from the 150's from the middle to the bottom is going to be horrendous. I have a 29" tall tank and run 400's at an 11" bulb height.

Hopefully others will chime in and offer their opinions as well.

 

[SENSIREEF]

Slow Cobra, do you have any information or details to back up your statements, or is this personal experience? I have seen a few charts done with bulb and par spread sheets. I have also seen tanks that are setup with 150W with higher end reflectors, which make all the difference in the world. Wattage in an overall majority is a big misconception, par and lumens are more important than wattage, this is an old theory practiced widely by many hobbyists, so maybe if he lowered his lights to about 6 inches off the water his tank would be fine. Just curious if you had any facts, other than opinions or personal advice. If so I would like to read up on it, and learn more as well.

 

[mxett]

If you have good reflectors like lumenarc, and you keep them within 4 inches off the water, they will suffice for most corals, as long aas your sps are kept high in the rockwork.

 

[SlowCobra]

Just the numerous readings on different lighting setups, par readings, etc found on here and Sanjays site. Not to mention the obvious which is... they make higher wattage lights for a reason. Tall tanks happens to be one of them. If there was no need for a higher wattage light on tall tanks why would anyone buy them and run up their electric bill more?

The only reflector that will help with the 150 is Lumenarcs or Lumen Brights(which currently are the subject of much debate).

Par and lumen run hand in hand with wattage. See previous statements about higher wattage.

Perhaps higher wattage MH's are merely snake oil and all of us have been fooled into believing we need the higher lighting to run our tall tanks.

Please show me your par and lumen data for a 150 at 3 ft. I am interested in seeing these results.