light placement in canopy

[belallanon]

For those with a canopy, how are your lights placed within it? I have to build a canopy for my 29g and was planning on using 1x175w MH in the center and some kind of VHO or PC suppments. However, my tank is 12" wide so I'm assuming that the canopy will not be much wider than this. If I place a MH w/ reflector on the lid, there is no place to put the supplements except on the sides. Do the supplements use reflectors also? Any help appreciated. Thanks much.

Randy

 

[belallanon]

Anyone?

 

[Anonymous]

The best way to distribute light in a tank of that size is to place the MH in the middle of the tank, perpendicular to the front. Most reflectors on the market (like those sold by PFO) tend to spread the light out perpendicular to the bulb. This should give you fairly decent distribution across the length of the tank. As for supplemental light, you should probably look at the smaller pc's - one one each side of the MH. Yes, you can buy/make reflectors for the PC's.

As a good exmple, of a similar lighting arrangment, look at the PFO rectangular pendants that use a single MH and a pair of PC's.

 

[smlacy]

I'm in the exact same situation, and read the instructions on my 175w spider reflector that said exactly what ghostofmilz said:

Mount the bulb perpendicular to the tank.

I assume that this means that the long dimension of the bulb is perpendicular with the long dimension of the tank. (i.e. socket facing directly towards the front of the tank)

Is this really true? I've never seen it done this way before, including in custom-made hoods. It will require significant trimming of the MH reflector. Right now its about 20" long, 13" wide, and fits well parallel with my tank. To mount perpendicular, I'll need to trim it nearly in half, to just under 12" in length. This doesn't seem wise to me, as it greatly reduces the amount of reflecting material. That means much more lost light, despite this recommendation.

I have the same problem as the one stated with mounting the PC or VHO supplimental lighting. My plan is to mount the supplimental lighting significantly lower than the MH bulb, possibly 2-3" from the tank surface, on a small "shelf" in the canopy. I may (or may not) trim the MH reflector to accomidate them.

Steve

 

[xrunner123]

Check out http://www.advancedaquarist.com/issues/ ... eature.htm
Someone did a spectral analysis of different reflectors, including parallel and perpendicular. Maybe this will be of use.

 

[Anonymous]

I'm in the exact same situation, and read the instructions on my 175w spider reflector that said exactly what ghostofmilz said:

Mount the bulb perpendicular to the tank.

I assume that this means that the long dimension of the bulb is perpendicular with the long dimension of the tank. (i.e. socket facing directly towards the front of the tank)

Is this really true? I've never seen it done this way before, including in custom-made hoods. It will require significant trimming of the MH reflector. Right now its about 20" long, 13" wide, and fits well parallel with my tank. To mount perpendicular, I'll need to trim it nearly in half, to just under 12" in length. This doesn't seem wise to me, as it greatly reduces the amount of reflecting material. That means much more lost light, despite this recommendation.

I have the same problem as the one stated with mounting the PC or VHO supplimental lighting. My plan is to mount the supplimental lighting significantly lower than the MH bulb, possibly 2-3" from the tank surface, on a small "shelf" in the canopy. I may (or may not) trim the MH reflector to accomidate them.

Steve

From my experience, very little light projects out from the end of the bulb, and the mogul end obviously projects none. Thus, that portion of the reflector extending beyond the ends of the bulbs has minimal impact on the overall light reflected into the tank. In any event, you can use some of the trimmed off material to close in the reflector adjacent to the end of the bulb if you want to minimize light loss. Or better yet, use the trimmed off material to make reflectors for the actinic lighting. FWIW, the PFO optimal reflectors that are designed to be mounted perpendicular to the front of the tank are only 12" long.

BTW, the actual length of the glass portion of the MH bulb is less than 12". My Iwasaki 400watt bulbs have glass length of 9.5". Thus, if you have room to allow your canopy to extend past the back of your tank, you can position your MH bulb so that the glass portion is centered over your tank. That will give you some space between the end of the bulb and the front, inside surface of the canopy where you can place a slightly angled piece of reflector material to reflect light down into the tank.

Mounting the PC's/VHO's closer to the water is not uncommon. The PFO light fixtures do it this way. In addition, if you look at the PFO Parallel reflectors, you will notice that they have L-shaped bends along the lowermost outside edges that are designed to accomodate PC's/VHO's.