Watts per gallon rule

Everyone says the reference point to get lights are base on watts/gallon.
My question is how tall does the tank has to be in order to use that rule.

Does 3 W/G become 6W/G when you place the coral in the middle. For example
if you tank is 18" tall and you place the coral at 9" will you double the
light on them? how about at 15" up?

I ask because I've been seeing those nano cubes with 18-30 watts with nice
coral set up.

TIA

Ruben

When you figure watts per gallon, you are figuring the
well being of everything in the tank at all levels. But
yes if you don't have as strong of a light you can move
the corals up higher, but it's just so much easier to to
have plenty of light, and not have to worry about moving
the corals higher to get enough light.

With lower light levels you can do soft corals instead of
the higher light corals.

Wayne Sallee
Wayne's Pets



RubenD wrote on 12/24/2006 4:45 PM:
Everyone says the reference point to get lights are base on watts/gallon.
My question is how tall does the tank has to be in order to use that rule.

Does 3 W/G become 6W/G when you place the coral in the middle. For example
if you tank is 18" tall and you place the coral at 9" will you double the
light on them? how about at 15" up?

I ask because I've been seeing those nano cubes with 18-30 watts with nice
coral set up.

TIA

Ruben

RubenD wrote:
Everyone says the reference point to get lights are base on watts/gallon.
My question is how tall does the tank has to be in order to use that rule.

Does 3 W/G become 6W/G when you place the coral in the middle. For example
if you tank is 18" tall and you place the coral at 9" will you double the
light on them? how about at 15" up?

I ask because I've been seeing those nano cubes with 18-30 watts with nice
coral set up.

TIA

Ruben


Ruben,

Watts per gallon is the worst measurement for light just because of the
reasons you list. It does not take into account the depth of the tank
or where in the tank you are putting the creatures.

What you need to look at is how much light the coral needs and how much
light you have. A nano cube with 30 watts of light (say a 12 gallon) is
only 2.7 watts per gallon or so, while my 180 with 2 400 watt lights is
4.4 watts per gallon. Both of which are very low according to the watts
per gallon rules of thumb. My 180 is setup as a SPS tank and really has
intense lighting on each end of the tank, with no light in the middle.
While my nano has moderate light on the whole tank.

As for the depth, you are correct in that if you move the coral up in
the tank you will increase the amount of light on the coral but you do
not change the watts per gallon.

Kim

Watts per gallon is the worst measurement for light just because of the
reasons you list. It does not take into account the depth of the tank
or where in the tank you are putting the creatures.

What is the best measurement for lighting then?

I supposed the coral under the bulb is the winner regardless of the
watts/gallon rule or the size of the tank, but how much light would be
acceptable? If I place the coral under the 30watts bulb, he'll be getting
not 6w but 30w, right?

What you think?

RubenD wrote:
Watts per gallon is the worst measurement for light just because of the
reasons you list. It does not take into account the depth of the tank
or where in the tank you are putting the creatures.

What is the best measurement for lighting then?

There is no good measurement for hobbiests. If you had the equipment
you could measure the par in different places in your tank and then see
if the coral you were looking at would survive with that amount of par.


I supposed the coral under the bulb is the winner regardless of the
watts/gallon rule or the size of the tank, but how much light would be
acceptable? If I place the coral under the 30watts bulb, he'll be getting
not 6w but 30w, right?

Close but not quite. If the light was a point light source, with a
perfect reflector then yes the coral would be getting all 30watts of light


The best thing I can say is post on here what size of a tank you are
setting up and what specific corals you want to keep and where at in the
tank you want to keep them.




What you think?




Kim

While the watts per gallon rule is not perfect, I find it
interesting when people knock it as being of no value, and
then they can't even come up with anything better.

Wayne Sallee
Wayne's Pets



kim gross wrote on 12/30/2006 5:51 AM:
RubenD wrote:
Watts per gallon is the worst measurement for light just because of the
reasons you list. It does not take into account the depth of the tank
or where in the tank you are putting the creatures.

What is the best measurement for lighting then?

There is no good measurement for hobbiests. If you had the equipment
you could measure the par in different places in your tank and then see
if the coral you were looking at would survive with that amount of par.


I supposed the coral under the bulb is the winner regardless of the
watts/gallon rule or the size of the tank, but how much light would be
acceptable? If I place the coral under the 30watts bulb, he'll be
getting
not 6w but 30w, right?

Close but not quite. If the light was a point light source, with a
perfect reflector then yes the coral would be getting all 30watts of light


The best thing I can say is post on here what size of a tank you are
setting up and what specific corals you want to keep and where at in the
tank you want to keep them.




What you think?




Kim

Wayne Sallee wrote:
While the watts per gallon rule is not perfect, I find it interesting
when people knock it as being of no value, and then they can't even come
up with anything better.


OK, here is something better - LUX, on a per organism basis. IE: This
acropora needs X lux, that maxima clam needs y lux, etc.

Then one can use any old light meter... er... make that any old WATER
PROOF light meter, to see if the spot they plan on placing the organism
in their tank gets enough light.

Next best thing after that would be lumens per gallon. (I know you said
lumens is percieved light (or something similar) a few posts ago, but
that ain't EXACTLY so. Lumens can be looked at measure of light output
in the visible spectrum -- more correctly called "luminent flux") Lumens
per gallon would indeed be better than watts per gallon.

I would even be OK with the watts per gallon were it to be based on the
radiant flux wattage of the light, rather than the electical consumption
of the light. In fact, this would be the best overall method, since it
would show the true light output of the bulb. But usually, when you see
"watts" listed with a bulb, they are talking about electrical
consumption, not radiant flux.

Wayne,

Someday you need to learn how to read. There is a good measurement that
will give usable info PAR or PUR, the only problem is that the tool to
measure it is to expensive for most hobbiests.

Watts per gallon is meaningless.


Let me give you an example. I setup a 125 gallon tank for a friend of
mine that has 150 watts of light on it. What corals can he keep in that
tank?




Wayne Sallee wrote:
While the watts per gallon rule is not perfect, I find it interesting
when people knock it as being of no value, and then they can't even come
up with anything better.

Wayne Sallee
Wayne's Pets



kim gross wrote on 12/30/2006 5:51 AM:
RubenD wrote:
Watts per gallon is the worst measurement for light just because of the
reasons you list. It does not take into account the depth of the tank
or where in the tank you are putting the creatures.

What is the best measurement for lighting then?

There is no good measurement for hobbiests. If you had the equipment
you could measure the par in different places in your tank and then
see if the coral you were looking at would survive with that amount of
par.


I supposed the coral under the bulb is the winner regardless of the
watts/gallon rule or the size of the tank, but how much light would be
acceptable? If I place the coral under the 30watts bulb, he'll be
getting
not 6w but 30w, right?

Close but not quite. If the light was a point light source, with a
perfect reflector then yes the coral would be getting all 30watts of
light


The best thing I can say is post on here what size of a tank you are
setting up and what specific corals you want to keep and where at in
the tank you want to keep them.




What you think?




Kim

RubenD wrote:
Watts per gallon is the worst measurement for light just because of the
reasons you list. It does not take into account the depth of the tank
or where in the tank you are putting the creatures.


What is the best measurement for lighting then?

I supposed the coral under the bulb is the winner regardless of the
watts/gallon rule or the size of the tank, but how much light would be
acceptable? If I place the coral under the 30watts bulb, he'll be getting
not 6w but 30w, right?

What you think?



Watts is not a measure of lillumination. LUX is the measurement of
illumintation. Lumens is a measurement of light output.

therefore it makes no sense to ask if a coral would be getting "30w" of
light.

The difference between lux and lumens can be illustrated thusly:
LUX will decrese with distance from bulb. How much a decrease there will
be needs to take many factors into account - distance from bulb, what is
in between (ie: water, glass, etc) and even the spectrum of bulb.

LUMENS will NOT decrease, since the bulb is still just as bright no
matter how far you are from it.

Lumens is how much light gets put out, LUX is how much light is reaching
what you are trying to illuminate.

What we SHOULD all be using is LUX. It would make sense to say things
like "this crocea clam needs about 32000 lux", but I have never seen
that used.

Add Homonym wrote:
RubenD wrote:
Watts per gallon is the worst measurement for light just because of the
reasons you list. It does not take into account the depth of the tank
or where in the tank you are putting the creatures.


What is the best measurement for lighting then?

I supposed the coral under the bulb is the winner regardless of the
watts/gallon rule or the size of the tank, but how much light would be
acceptable? If I place the coral under the 30watts bulb, he'll be
getting
not 6w but 30w, right?

What you think?



Watts is not a measure of lillumination. LUX is the measurement of
illumintation. Lumens is a measurement of light output.

therefore it makes no sense to ask if a coral would be getting "30w" of
light.

The difference between lux and lumens can be illustrated thusly:
LUX will decrese with distance from bulb. How much a decrease there will
be needs to take many factors into account - distance from bulb, what is
in between (ie: water, glass, etc) and even the spectrum of bulb.

LUMENS will NOT decrease, since the bulb is still just as bright no
matter how far you are from it.

Lumens is how much light gets put out, LUX is how much light is reaching
what you are trying to illuminate.

What we SHOULD all be using is LUX. It would make sense to say things
like "this crocea clam needs about 32000 lux", but I have never seen
that used.


As I stated in another responce on this thread. There is a problem with
lux. It does not weight the light according to photosythisys, IE yellow
and red add to lux but do not add much to photosynthisys. But it is a
much better measurement than watts per gallon since as long as you know
the spectrum of the lights or you are using a full spectrum light source.

Kim