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Re: lighting questions

Dgrim62 at cs_com wrote:

> Hi everyone,
> Not being an expert this subject, I'd like some opinions from some of our
> members who know about lighting.
> I have three heavily planted tanks:
> 1. A 125 gallon 72" x 18" x 24" lit by two 6 foot VHO daylight bulbs (URI
> Aqua-Sun 10K) totalling 320 watts or 2.56 watts/gallon.
> 2. A 65 gallon 36" x 18" x 24" lit by two 3 ft VHO daylight bulbs (URI
> Aqua-Sun 10K) totalling 190 watts or 2.92 watts/gallon.
> 3. A 90 gallon 48" x 18" x 24" lit by a Custom SeaLife Brite Lite 2 x 55 watt
> PC Ultra Daylight bulbs (8800K) totalling 110 watts or 1.2 watts/gallon.
> The 90 is the newest, being about a month old. The plants in all three tanks
> have roughly equal light requirements. The most light loving plant I have is
> probably glossostigma or pygmy chain sword. My question are regarding the 90
> gallon. The plant growth is great. The glosso is growing as a ground cover
> and not reaching for the light. Pygmy chain sword is sending out runners all
> over the place. The swords are all sending stalks out. The greens in this
> tank are the most pleasing to the eye of all 3 aquariums. Yet this tank has
> less watts/gallon than any of the three . All receive the same additives and
> are CO2 injected. I originally thought I'd need another Britelite to get the
> same watts/gallon as in the other tanks, but it looks like I may not need it.
> None of the plants in the 90 look under illuminated to me. All three tanks
> have a misture of swords, apons, crypts and a few oddball plants. Few stems.
> Pretty standard fare.
> If this tank continues to do well I am thinking I might get rid of the VHO
> hoods I have on the 65 sand 125 and just go with a lower wattage BriteLite
> like I have on the 90. Less heat and less electricity consumption. I'll
> observe for a few more weeks since the 90 is  so new.
> Any thoughts. Anyone with similar experiences?
> Regards,
> Dave

Watts/gal is just a rule-of-thumb that works best when you compare apples
with apples. VHO bulbs are roughly 40% less efficient than PCs, in terms of 
lumen/Watt (or PAR/Watt for the purists). Aside from that, I believe the 
Britelite strip has a very nice aluminized, curved reflector inside. I don't 
know about your VHO hoods, but if they have anything else as reflectors (such
as white paint or a flat aluminized surface), you can add another, large 
efficiency difference in between your VHO and PC fixtures. In the end it might
be that all your three tanks are getting similar amounts of ligth.

- Ivo Busko
  Baltimore, MD