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Re: A couple of questions....about Dupla availibilty and MH vs Flourescents..

>       I am curious about the economics of running a MH setup over this
>tank. One I noticed
>        is that a 5' tank is a odd size for lighting. I also like the idea
>of pendant lighting since
>        I have plants growing in and out of the tank. My philodedrum grows
>all over includ -
>        ing the light box.

You could probably light your 5' tank with only two fixtures if you hung
them high enough that the light spread would overlap in the middle. 3
fixtures would spill over on the ends. For a 6' 3 175 watt fixtures would
be ideal, but if you're using only 2 on a 5' you would probably want to use
250 watters hung higher than normal (18+ inches). MH is idea for open top
tanks when you want a lot of room between the water surface and the lights!
You can focus the MH light into your tank easier with a smaller reflector
than for flourescent, and you maintain enough intensity to "punch through"
the water.

>        I have read a heap but was hoping to get some personal/informed
>opinions on :
>        1) Cost of setup for MH ( 2-3 lights for 5ft)

Depends on the fixture :-) For commercial setups you are probably looking
at $200-$400 per fixture, with the low end being a retrofit kit which is
somewhere between commercial and DIY, and the high end being the very
expensive (but apparently very good) Giesemann fixtures. If you use the
Giesemann fixtures remember that they use the HQI MH bulbs so you won't
have the same selection of bulbs available that you would with a more usual
mogul-base system.

You can DIY a system for a LOT less. I've mentioned in some other threads
that my triple 175watt system was about $90 for the ballasts, sockets, and
enclosure (I already had the high-temp wire). It was probably around $200
when you include the reflectors. I doubt any commercial system can be had
for that.

>        2) On going costs... bulb replacement period

My 400 watt fixture gets about 3 years of bulb life running 14 hours a day
(that one is over terrestrial plants). It is not as bright at the end of
that time, but it is still a pretty potent lamp that does a good job
growing the tomatoes under it. I haven't lost any 175 watt bulbs yet and
they are still going strong after one year.

For me the biggest on-going cost is electric. We have about 10.5 cents/kH
here, and the coil ballasts throw out about 20% of their input power as
heat (400 watt draws 480 watt, 175 watt about 210 watts). The single 400
watt is about $20/month to run, the 175's (three of them) are a little over
$30/month. For a while I was looking at lighting a marine tank with four
400 watt fixtures but that would be $70/month in electric. 

>        3) Quality of equipment

Depends on the equipment. Most of the commercial fixtures I have seen use
similar components, so I would suspect that the quality is similar. The
primary concern would be reflector design and longevity, IMO.

>        4) general annoying things about MH that nobodies tell you about.

The ballasts *can* be noisy. I've been lucky and had fairly quiet ballasts
myself. Using the coil ballasts power interruptions can extinguish the
lamps for longish periods. For me, a power interruption of more than 1/2 a
second or so (long enough to extinguish the arc completely) will result in
the lamp remaining off for 10-15 minutes until it restrikes on it's own. It
will restrike faster if I manually power cycle it, but that is a pain and
I'm not usually around to see the problem. You can hear the things strike
too -- the ballast makes a "thung" noise every time it strikes until it
holds, and while it's doing this the light is a bit like a strobe light
with a few bright flashes. After the initial strike it gradually builds to
full intensity over a minute or so. There is a color shift while it does
this, starting bluer than normal and working it's way to a normal color.

Ballasts will occasionally self-destruct from the heat. What usually
happens is a winding shorts, you pop a fuse (you should *have* a fuse on
it), and then you need a new ballast. It's a rare occurance, but it does
happen. Fans might help, but I haven't had fans on my ballasts long enough
to say for sure.

Overall I have been very happy with MH lighting. It is the ultimate plant
light, IMHO :-)


Waveform Technology
UNIX Systems Administrator