Re: Lighting for 2' deep tank

> I want to make sure I got it right and hope knowledgeable peoples
> on this list would help. I'm doing preparation for the 2ft deep
> 120gal tank I'll be getting in the next few months. I was reading
> the august issue of Fishkeeping Answer (a British mag) and they
> mentioned that only MH or MV lamps are recommended for 2ft or deeper
> tanks. Flo tubes are for depth of 18" or less. Is this true or could
> I get away with only flo bulbs? As the lighting would be costly, I want 
> the lighting to be absolute and would not want to have to change it 
> later on. Thanks in advance for any help.

I have a 48" 4-bulb Coralife hood over a 2' deep Booth-onian tank
(90g) giving me 160w.  At first I tried a combination of 2 Tritons and
2 Vita-Lites, and things went well for several months. I successfully
grew a wide variety of plants, some which supposedly need intense
light (e.g. Rotala sp.). As the bulbs aged, however, I noticed growth
rates and quality of growth decreasing. I switched in 2 new Tritons
and things got better immediately.

My very subjective opinion on this is that with 4 T-12 bulbs over a 2'
tank you're very close to the minimum required for high-light plants.
When I changed bulbs I especially noticed a change in growth with my
E. tenellus which made me suspect light intensity as the problem.

Several months ago I set up a 2' deep 35g hex tank (automated pH
controlled CO2 / Dupla additives / no heating cables) with a single
Coralife 175w 5500k MH pendant.  I love this lighting system! Why?
Because it gives me a great deal of freedom to experiment with light
intensity over the tank. Lowering or raising the pendant to vary
things is a piece of cake (right now it's ... hmmm, where's that tape
measure ... 7" off the water. With a 5 month old bulb.). Even if you
don't want to experiment with things, it's nice to be able to lower
the bulb as its intensity drops off with age. And *all* of the plants
are doing very well. (If I ever get off my lazy a** you'll see photos
of this tank appearing somewhere Real Soon Now.)

They MH pendants are bloody expensive, however.

Dan Resler

Dept. of Mathematical Sciences            
Virginia Commonwealth University           
Richmond, VA                                    
23284-2014 USA
email: resler at liberty_mas.vcu.edu