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RE: T5 Wattage

> Question about T5's:
> LFS was selling some 18" T5 bulbs w/ disposable ballasts for $20 per
> bulb and ballast. The problem was that even though each bulb was
marked 13W, 
> proprietor maintained that wattage was equivalent to that of a 55W
compact fluorescent 
> and that two 13W T5's would suffice for a 29 gallon tank. Does anyone
have any insight 
> as to what he may have been talking about?
> Victor

I have looked at some T5 bulbs lately and although I am not real
familiar with them I have found a few websites for them.  Try Osram's
site (http://www.osram.com/purchasing_portal/index.html and
zc=) Philips' site
ACT&lan=EN+&ecu=LMP|PHL|EP&tree=0&t=0#).  There are probably other
manufacturers that have similar products in their line.  I just have not
been able to locate them on the web.  E-mail off list and I will forward
a copy of the Osram chart if you would like.

Mostly I have found that they do not have information on the higher
temperature bulbs (>4000ēK) here in the US.  You have to go to the
German websites to find them.  This seems to be true of the CF's too.  I
also noticed that when you drill down on the second Osram link above to
G5 cap T5s they refer to the 13W T5 as "Old 4-13". 

One catalog sheet I found at the Osram site indicates they make a couple
of 13W T5's but most are either outside the ēK range and/or CRI most
people here would consider acceptable.  They do have a L13W860 (8 is for
80-90 CRI range, in this case 85 and 60 indicates 6000ēK) that their
chart indicates puts out 860 lumen but this is a 20.6" T2.  Philips did
not seem to have any either.  I searched both their US sites and was not
able to find anything with an appropriate temperature.  As I said before
most everything I have found is down in the 2700-4000ēK range.

Using the 2-3W/gallon rule (that virtually everyone disagrees with but
seems to use anyway as a general guideline) 26W seems a little light for
that size tank.  IMO - unless these bulbs put out an incredible amount
of Lumens/watt, you would need more light.  A 55W CF bulb with a good
reflector (1.9 watt/gal) or a couple of 36W CF bulbs with good
reflector(s) (2.5 w/g) would seem to be a better choice.  I have had
good luck with AH Supply (www.ahsupply.com) and there are others.  If
you want to use T5s, they make some about 21" long 24W HO bulbs you will
find on the Osram and Philips sites.  Three or of those would give you
2.5 w/g and with 4 you would have 3.3 w/g.  Osram has two suitable 24W
HO bulbs:  Lumilux FQ24W/860 (1600 Lumens, 6000ēK, 85 CRI) and Lumilux
de Lux FQ24W/965 (1300 Lumens, 6500 ēK, 95 CRI).  With the appropriate
ballasts these T5s are dimmable to anywhere from 1-100%.  I have been
told that the manufacturer swears this does not have any adverse affect
on the bulb (output, longevity etc.).  There are also some US
manufacturers starting to come out with this stuff too.

Keep in mind that a lot of this depends upon how much light what you are
trying to grow needs.

Hope this helps,