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90G Lighting

> On June 4, David Thomas Gauthier wrote:
> I am doing a DIY hood for a 90 g (48X18X24), and have gone through the most
> recent lighting documents on the Krib.  I am planning on installing T8 48"
> tubes (Staybright 850s), and am wondering whether to got with 4 or 6.  From
> what I read, I assume the former would give me around 2 w/gal, while the latter
> would give me around 3 w/gal.  Problem is, my price goes up quite a bit if I
> need 6 tubes, as I would need two ballasts rather than 1.  So, if 4 would be
> adequate, that would be preferable.  Vegetation will be primarily SE Asian
> (Crypts, Anubias, Java).  Has anyone had success with 4 tubes over this size
> tank, or should I go ahead and buy the extra ballast?  Thanks.


I am in the process of setting up a similar size tank, a 75G to be exact, and I plan
to use 4 T8 lamps.  The one additional thing I do plan to do is to add a highly
polished reflector.  These are available from lighting wholesalers and are used in
retrofits of fluorescent fixtures in commercial lighting applications.  The building
where I work was just redone late last year, and while the lighting contractor was
there I asked about the price of the reflectors, and he thought they were around
$8.00 or so.  That price may reflect a high quantity price, but even if the price
were double for small quantities, it would be well worth the investment.  I don't
have the exact figures, (maybe someone else out there does) but for some reason a
30% increase in light output from the use of the reflector seems to stick in my

Another reason I plan on using just the 4 T8 lamps is from my experience with my
last planted aquarium.  It was a 55G and I used 2 48" T12 Triton lamps with an
electronic ballast and a DIY polished aluminum reflector in a DIY hood.  I had great
results growing a wide variety of plants, including all the varieties you mention,
as well as many south american swords.

If you still are not sure 4 T8 bulbs will be enough, just lay out and pre wire 2
extra sets of bulb sockets in the hood.  Try it with 4 T8 bulbs and the reflector
first, and if you don't think the output is high enough, it will then be a simple
matter to add the additional ballast and the 2 extra bulbs.

Another thing to keep in mind when making your "watts per gallon" calculations is
that the newer generations of fluorescent lamps, especially T8's, are more efficient
than the T12's they replace.  For example, the GE Staybright T8 you mention as
planning on using is a 32 watt tube in the 48" length, and has a mean lumens of
2830. That works out to 88.44 lumens per watt. The T12 version of the same bulb is a
40 watt tube, and has a mean lumens of 3050.  That works out to 76.25 lumens per
watt.  With the more efficient T8 bulbs, it is a good idea to keep the total lumens
figure in mind as well as the "watts per gallon".  Also keep in mind that "watts per
gallon" is just a "rule of thumb" and is not "written in stone".

BTW, for those who are interested, the above "mean lumens" figures came from the
Graingers catalog.  They may be a little expensive, but their catalog sure comes in


Jay Bickford
Savage, Minnesota