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Re: lighting question
> Date: Thu, 06 Dec 2001 13:38:03 -0800
> From: "Roxanne Bittman" <rbittman at dfg_ca.gov>
> Subject: lighting question
>
snip...
>
> I'm interested in more light - what's the next step up from 3 watts/gal using standard
> T-12 fluourescents?
Not much, if you want T-12s. Dump the LFS bulbs and get a mix of "Chroma 50"
(Sunshine) and "Daylight" commercial tubes. They will hold 90% brightness to
the point they won't strike any more. Their lumens/Watt are down, because they
have the wider spectrum plants can use.
Two small upward steps involve going to a smaller diameter tubes (T-8, T-5 --
aka power compact) and reflector shape. Most aquarium hood reflectors really
are not shaped well to force a lot of light straighter downward, so it enters
the water gracefully.
With larger tubes, a major percent of the light can be lost in what is called
"restrike" if you have enough bulbs in there to actually get the wattage. Flat
reflector areas above the tubes are nearly 100% waste. Not only can more light
get past thinner tubes, they tend to be brighter and more efficient, too.
The standard tank shape just does not have sufficient surface for really
efficient use of the output of T-12 tubes. Most of us have discovered that.
T-12 and T-8 sockets are the same, so change your ballasts (that sound
marginal, anyway) if they will not drive T-8s to full brightness.
Few of us have the reflector design skills or access to sources of really good
reflective material. Polished aluminum looks very pretty, but it is pitifully
lossy, if more than one bounce (15%+ loss when near perfect) is involved. You
want 95%+ reflection at a 90 degree+ range of angles (at least +/- 45 degree
angle of incidence/reflection).
Enhanced reflection coatings, like the late 3M Silver Bright, or the German
stuff used by AH Supply is very hard to find in the US any more. It is hard to
get better than the AH Supply kits, unless you want a very high, boxy hood.
[Those go up considerably more than the one step up you asked about, tho.]
Get some good Lithonia commercial "troffers" (used for store and office
ceiling fixtures) and put the designed number of T-8s in them for that
first-step-up improvement. Unfortunately it may cost more than the AH solution
and give less light/$. Be sure to check the difference, first.
That's my US$0.02, anyway.
Wright
PS. I have found that polished aluminum reflectors are actually worse than
potato-chip bags (metallized poly) shaped properly, for use over small tanks
with PCFs. :-) 36W PCF over a 10G tank really zings! Fantastic algae blooms!
--
Wright Huntley -- 650 856-4245 -- 879 Clara Dr. Palo Alto CA 94303
The San Francisco Bay Area Killifish Assn. (BAKA) has a new web
site at: http://www.sfbaka.net. [I'm the proud Web Poppa.]