Re: Lighting for a 120g tank (fwd)

I assume this was intended for the list.

Shaji Bhaskar, Durham, North Carolina                   shaji at nando_net

---------- Forwarded message ----------
Date: Tue, 9 Jan 96 10:23:04 PST
From: Stephen.Pushak at saudan_HAC.COM
To: KB_Koh at ccm_ipn.intel.com
Cc: Aquatic-Plants-Owner at actwin_com
Subject: Re: Lighting for a 120g tank

kb koh wrote:
> >Well, we discussed how light is refracted/reflected inside a tank
> >which means the inverse square law does not apply once the light
> >has made it inside the tank. You could use FL lighting to get your
> I followed the discussion at length in r.a and from there it seems that 
> eventhough the inverse square law does not apply, there are too many 
> objects in the tank such as plants that decrease the available light 
> significantly by the time it reach bottom of the tank.

true. we often compute watts/gal and it seems to be a good measure
since it takes into account the volume used by plants and the
upper and lower areas in a deeper tank. It was also discussed on
the APD at length for a while.

> >I thought I would want two pendants but the more than double costs
> >for this arrangement dissuaded me. The 250w lights a tank with a
> >width of 4' with no problem at all. The lower wattage MH systems are
> >less efficient and cost more since they are not commonly used. The
> >250w+ bulbs are used very commonly. I get my ballast and equipment
> I thought that too since the article suggested using one pendant for 
> 18-24" of tank length. 48" would requires 2 pendants.

I find no problems with a single pendant. :-)

The light is very bright and the ends of the tank also get good strong
light due in part to the reflection from the tank ends. It also makes
a good spot for the Crypts and sword plants which don't need as strong
light and may be troubled initially by red brush algae. I have to grow
tall shade plants and use floating plants to reduce light intensity 
for the crypts. The notes I had seen indicated that MH can effectively
light 4'x4' areas. Some light will spill out the front and back. The
light from the back side hits the wall and provides a fair amount of
ambient room light. The reflector fixture needs to be deep enough
that it won't glare in your eyes. Initially I used tin foil and
scotch tape until the second reflector was made since they only
had a shallow reflector on hand for a while. I have two tanks lit by MH.

A single fixture of 100w costs more than a 250w since each bulb 
requires it's own ballast and the 100w bulbs are less commonly used
and have a lower CRI.

> I'm not sure if I can get the parabolic reflector as most MH lighting I 
> saw shaped like the one used for lighting the tennis court. Even the one 
> sold at a marine fish shop.

That might be a problem. You may need to search other places for that
item. An alternative might be to construct a reasonable fixture from
aluminum although it wouldn't have the nice parabolic shape. There
should be vent holes drilled at the top for air circulation and I
like to paint mine flat black on the outside. The inside should be
reflective of course.

> How do you mount the pendant? Is it from the ceiling or a stand? If I go 
> with MH, I plan to use a stand mount onto the aquarium stand. Also the 
> tank would not have a cover, have you got any problem with fish jumping 
> out? Thanks.

I use a butterfly type hook designed for hanging home light fixtures
and drill a 1" hole in the ceiling for the hook. The fingers of the
hook are spring loaded and latch out as you tighten the screw on the
hook. The fixture must be securely mounted. I use metal chains to hang
it which are just attached by screws to the fixture.