what a difference two inches make!! - The Planted Tank Forum
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post #1 of 6 (permalink) Old 06-04-2006, 08:09 PM Thread Starter
Algae Grower
Join Date: May 2006
Location: norman, ok
Posts: 24
what a difference two inches make!!

a 40 gallon breeder tank has dimensions 36x18x16. a 50 gallone has dimensions 36x18x18. A 96 watt AHS light over the 40 will give 2.4 wpg, while the same light will give 1.92 wpg for the 50 gallon. these two tanks have the same footprint, the 50 gallon is just 2 inches taller. I have heard that wpg is not always the best measure of light, this situation is obviously one of them. Does anybody have any tips on evaluating this lighting matter?

putting the light 2 inches higher is not that drastic a shift. any thoughts?
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post #2 of 6 (permalink) Old 06-04-2006, 09:24 PM
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Location: Indiana, PA
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For starters, a 40 gallon breeder is not 40 gallons and a 50 gallon breeder is not 50 gallons. Tanks are just sold as a ___ gallon for a rough guideline.

You're right, WPG is not the best way to evaluate lighting as this very situation shows. My opinion is that footprint matters more than gallons. Yeah, not if you're comparing a 12 inch tall tank to a 28 inch tall tank, but in general.

For either of these tanks, I would say that 96 Watts is enough light for low to medium light loving plants, but it may not be good enough coverage.
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post #3 of 6 (permalink) Old 06-04-2006, 11:15 PM
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A 40 breeder actually holds 43 gallons of water as I recall. And the 50 holds around 47-48 gallons. The 30 and 40 breeder tanks are the only two aquariums that actually hold more water than the size indicates.
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post #4 of 6 (permalink) Old 06-05-2006, 03:47 AM Thread Starter
Algae Grower
Join Date: May 2006
Location: norman, ok
Posts: 24
as far as coverage goes, what if i put the light dead center, with a white background (or something)? would the ahs reflector help in the way of getting the light to the front and back?

i could always put the high light plants in the back/middle and lower light plants in the front.
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post #5 of 6 (permalink) Old 06-05-2006, 02:30 PM
Algae Grower
Join Date: Oct 2004
Location: AZ
Posts: 132
I have a ah supply 96w over a 40 breeder and its scary bright you really have to see these lights and reflectors to appreciate them it really is amazing!!

I was able to grow all medium light plants in their just fine i also seemed to be able to maintain the red of most plants. Of course in my experience Co2 for this light level helped and ferts without the Co2 i had a very algified tank lol

Starting back into the Hobby!
Setup my 55g with 108w T5HO and co2 and augmented pool sand. Converted from Fish only.

Planing a 65g Tall done right from the start using Tom Barr's Non-Co2 Method now I just need to figure out the lighting!
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post #6 of 6 (permalink) Old 06-05-2006, 05:03 PM Thread Starter
Algae Grower
Join Date: May 2006
Location: norman, ok
Posts: 24
is it a ahs 96 watt light by itself? your tagline says 130 watts.
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