Re: more about e-ballasts

> About 3 months ago purchased a retrofit kit, 2 Aqua Sun VHO bulbs and the
> smaller IceCap ballast for my 55 gal planted tank.  Then, feeling sorry for
> my tetras when they were blasted by 220 Watts of light at 6:00AM, 

It gets their hearts goin'.  ;)

>I installed the new dimmer designed by Niche Engineering.  I highly recommend
> this setup to anyone.  Its not cheap, but after installing a ground plane
> on the flourescent lights they turn fully on and fully off over a one hour
> period.  The fish love it and the effect is asthetically pleasing to watch.

Is this the dimmer rig that Champion sells?  

> One question:
> What is the life expectancy of these bulbs operating with the IceCap?
> Anyone have any experience with them?

My friends run actinic lamps for 8 months to a year if they are within an
acrylic shielded light hood.  You will get some falloff in intensity over
that period, though.  There is an unsubstantiated "thought" that without
some shielding being present, fluorescent lamps driven at VHO power may
eventually develop pinholes in the phosphor and start bleeding some fairly
energetic UV into the tank.  The "foundation" for this speculation is the
observation by many that their corals tend to get light in color (less
brown = bleach = loss of symbiotic algae) after unshieled VHO lamps have
been in service 3-6 months.  The color associated with symbiotic algae 
goes back to normal levels after a lamp change.  This is exactly the 
opposite direction that one would expect if the effect were due to PAR 
(photosynthetically active radiation) or visible light.  Corals will get 
lighter in color when hit with more intense than usual PAR.  We expect 
the PAR output of the lamps to be monotonically decreasing with time, so 
the corals should get darker, not lighter.  UV has been shown to cause 
coral bleaching, so the effect is preliminarily chalked up to increased 
UV output with time.  The hypothesis is somewhat reasonable, because one 
can often discern some changes in the phosphor with time, and because 
without the phosphor, fluorescent lamps are essentially low pressure 
mercury lamps.  Their main output is at 254 nm, which is germicidal UV.  
There are several other longer wavelength UV lines in the Hg emission 
spectrum that could also cause problems.

Aquatic and terrestrial plants are also susceptible to UV.  Any
photosynthetic system is susceptible to UV.  Athough with the amount of
humic acid present in most freshwater planted tanks, the water itself
should be a very effective UV filter. 

If any of you are interested in a discusion of the effects of activated
carbon treatment on visible and UV light transmission in a marine tank, I
have an article on the subject in the.... summer 95 issue of Aquarium
Frontiers.  Although the article describes a coral bleaching phenomonon in
a reef aquarium, it is likely that one could observe similar effects in a
planted tank if there was a rapid change in water color caused by a water
change or activated carbon treatment, AND if the lights were producing a
substantial amount of UV. 

Watch your plants.  They will tell you if there are problems.

So, in answer to your question about lamp lifetime, between 3-12 months, 
depending on the amount of shielding humic acids are giving your plants.
If you have either an acrylic or glass lens, ~12 months, if you and the 
plants can tolerate the decrease in visible and PAR light, respectively.

I'm trying to get someone with UV probes to look at some aged VHO lamps 
to test this idea.  We may have the answer in a few months.