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Re: Aquatic Plants Digest V2 #639

>Date: Wed, 9 Apr 1997 20:45:41 -0700
>From: Paul Nicholson <paul at eisusa_com>
>Subject: Re: Lighting question. . .
>At 15:39 -0400 4/9/97, :Edziu Iskra  wrote <edziu at cybernex_net>:
>>I have some extra 12-v mini-halogen fixtures that I've been contemplating
>>using on my plant tank. . .

>They will work fine, however Halogen effiency is poor compared to
>flourescent. After all there incandescent bulbs with a halogen gas added to
>prevent filament deposition inside the envelope.
>Halogens generate a lot of heat, and you have to figure the ineffiency of
>the transformer if you use a 12 volt unit. A 120 volt unit should be just
>as efficient for a given filament temperature. A 12 volt unit may be able
>to sustain a slightly higher filament temperature because the filament can
>be much shorter and thicker, therefore it is mechanically stronger. A 120
>volt filament is fragile, and hence the designer may elect to run the
>filament a little cooler for mechanical strength reasons. Otherwise the
>effiency will be the same.

My understanding, albeit from a non-technical source (a non-aquarist
lighting design manual which did not go into technical specs {meant for
contractors and designers}), was that in terms of lumens per watt, a 12v
halogen system was markedly more efficient than a 120v system.  From my
understanding of lighting systems, I believe this efficiency may have to do
with the fact that 5 20 watt incandescent bulbs will produce more lumens
than 1 100 watt bulb.  Apparently, this effect overcomes the necessary loss
of running the transformer, so that, in sum, a 12v system is significantly
more efficient than a 120v.  If anyone can explain where my reason is wrong,
please do so, and if anyone can find lumens/watt or similar ratings for 12v
vs. 120v systems, please do.


>Date: Wed, 9 Apr 1997 23:02:54 -0700 (PDT)
>From: "A. Inniss" <andrewi at u_washington.edu>
>Subject: Curious algae: Will Ghost Shrimp eat it?
>It is bright green,
>grows primarily amongst my floating plants (Ceratopteris pteridioides),
>though it will also in my Java moss near the surface.
>	I'm wondering what this algae might be, and whether Ghost shrimp
>would be likely to eat it.  In fact, what kind(s) of algae do Ghost shrimp
>like, if any?

I've never seen ghost shrimp more than an inch or two up into my plants;
they prefer to scavenge along the bottom.  They're not really swimmers,
except to bolt away backwards when scared.  I've never seen them go after
algae proper, either.  They do a fine job, however, of picking between
stones, gravel, roots, etc, and generally keeping things clean.  Between
them and the cories, there's little left on the bottom for the SAE's, who
then go after the algae.  I have heard that they will consume cyanobacteria,
however (blue-green algae.)  I've never had any (knock on wood.)

>And do they require water to be a little harder than the
>aggressively soft water they have here in Seattle?

I don't know for certain, but I believe the answer is no.  You might be
mislead by their shells -- the shells actually are chitinous, not calcerous,
so, unlike snails, they don't need a particularly large supply of calcium.
Unless, of course, I'm wrong.  8)