I have a 20-gallon TALL tank that I am going to plant. I plan on getting a
light kit from AH Supply, but I'm not sure what I should get to light this
tank. I know I'm gonna need a lot of light since the tank is so deep, but
beyond that, I'm clueless as to how much light I'll need. Any suggestions?

thanks in advance,
jim

2 watts per gallon is a good rule of thumb, depending on what you're putting in
it. If you are using low-light plants like java fern, 20-25 wats would likely be
ok. Now if you have high-light plants (like cabomba) you should have 40+ watts.

--
Billy
ABSURDITY: A statement or belief manifestly inconsistent with one's own opinion.
"I know of no time which is lost more thoroughly than that devoted
to arguing on matters of fact with a disputant who has no facts,
but only strong convictions." (James E. Thorold Rogers)
"Zerex" wrote in message
...
: I have a 20-gallon TALL tank that I am going to plant. I plan on getting a
: light kit from AH Supply, but I'm not sure what I should get to light this
: tank. I know I'm gonna need a lot of light since the tank is so deep, but
: beyond that, I'm clueless as to how much light I'll need. Any suggestions?
:
: thanks in advance,
: jim

oaway (Zerex) wrote in
:

I have a 20-gallon TALL tank that I am going to plant. I plan on
getting a light kit from AH Supply, but I'm not sure what I should get
to light this tank. I know I'm gonna need a lot of light since the
tank is so deep, but beyond that, I'm clueless as to how much light
I'll need. Any suggestions?

From http://faq.thekrib.com/ (note, though not mentioned at the
website, measure your surface area and light depth in inches):

When calculating the amount of lighting you will need there is a general of
thumb. First multiply the surface area of the aquarium by the distance from
the light source to the top of the gravel. Then depending on the type of
plants you desire multiply this by one of the factors given below.


Low light plants 0.08
Low to Moderate light plants 0.12
Moderate to Bright light plants 0.18
Bright light plants 0.27

This will give you the ideal watt hours of fluorescent lighting that you
need. Divide this number by 11 and you now have the approximate total
wattage of lights you need. Unfortunately this number may not be equal to
what is available in bulbs so find the combination of wattage that will
most closely match this requirement and adjust the available time to match
the watt hour calculation.
Example

I have a 20-gallon TALL tank that I am going to plant. I plan on getting a
light kit from AH Supply, but I'm not sure what I should get to light this
tank. I know I'm gonna need a lot of light since the tank is so deep, but
beyond that, I'm clueless as to how much light I'll need. Any suggestions?

Go with the 55W if you want a thick foreground, otherwise the 40W would be
better. I'm running the 1x55W over a 15gal, its really strong light.... I
would highly recommend a compressed CO2 system; I was unable to keep things
under control with DIY CO2 and the 55W.... 5000 or 6400k, stay away from
10,000k bulbs and actinics

Cheers,
Jeff Ludwig

This will give you the ideal watt hours of fluorescent lighting that you
need. Divide this number by 11 and you now have the approximate total
wattage of lights you need.

Hmmm... This seems to be a problematic formula. Example: 6' x 2' x 2' tank.
Surface area: 1728 square inches
Distance from gravel to light source (pendant light): 30"

The formula is for flourescent lights. It doesn't apply for MH lights.

But yeah, this is like the "watts per gallon" rule. It's only a rule of thumb.
It only takes tank volume into account. It doesn't take into account that
tank depth can matter more than the surface area. Less than 2 wpg may be fine
for a tank that's only 12" deep, but not for a tank that's 24" deep.


Leigh

http://www.fortunecity.com/lavender/halloween/881/

"LeighMo" wrote in message
...
This will give you the ideal watt hours of fluorescent lighting that you
need. Divide this number by 11 and you now have the approximate total
wattage of lights you need.

Hmmm... This seems to be a problematic formula. Example: 6' x 2' x 2' tank.
Surface area: 1728 square inches
Distance from gravel to light source (pendant light): 30"

The formula is for flourescent lights. It doesn't apply for MH lights.

Sure. But, even when I assume that the light source is floating on the
water surface, we are still *way* out: I get 3.7W per gallon for
a moderate to high light level tank.

But yeah, this is like the "watts per gallon" rule. It's only a rule of
thumb.
It only takes tank volume into account. It doesn't take into account that
tank depth can matter more than the surface area. Less than 2 wpg may be
fine
for a tank that's only 12" deep, but not for a tank that's 24" deep.

Agreed. But I still take issue with that formula. The numbers that pop
out are *way* off -- too much to be useful even as a rule of thumb.

Cheers,

Michi.

--
Michi Henning Ph: +61 4 1118-2700
Triodia Technologies http://www.triodia.com/staff/michi

Sure. But, even when I assume that the light source is floating on the
water surface, we are still *way* out: I get 3.7W per gallon for
a moderate to high light level tank.

It's probably not applicable for a tank the size of yours. But I think it's a
reasonable figure for "normal" sized tanks. Say, between 10 and 100 gallons.
Most people who want a "bright" tank aim for 3-4 wpg.

I have a 75 gallon tank. 48"x18"x18" (top of the gravel to bottom of light).
There's 250 watts of PCF light. Plugging in the numbers gives me a value of
0.18 for 11 hours...exactly what they recommend for a moderate to bright tank.
Which is what I would consider this tank to be. It's more than moderately lit,
but not really bright -- plants like Lilaeopsis grow slowly.

However, I'm not sure it's worth doing all the math; this formula is clearly
just a fancy way of getting the watts per gallon rule of thumb. There's a
linear relationship between volume and lighting (which a different Krib article
claims is breaks down for both very small and very large tanks).


Leigh

http://www.fortunecity.com/lavender/halloween/881/