Watts per gallon rule

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

Add Homonym wrote:
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.


Lux and Lumens are not great either, only because they do not weight the
light for photosynthisys. Not all light colors are equal when it comes
to photosynthisys. That is where PAR and PUR comes in. Only problem is
the cost of the devices to measure PAR and PUR

Kim

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

Since you think that watts per gallon is not the best way
to go, then tell us what method that *you* think hobbiest
should use?

Please define this in such a way that any hobbiest can use
your method to see if they have enough light :-)

Wayne Sallee
Wayne's Pets



kim gross wrote on 1/4/2007 6:00 PM:
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

The lfs here does not go by watts per gallon either. Its something
along the lines of watts per inch or something like that. He was
trying to explain it to a person one day and I overheard him and it
totally confused me.......I'll have to see if he can give me a
condensed version of what he was trying to say. I really do not have
issues with lights as I tend to lean to critters that do not require
such intense lighting. There is more than enough corals to create a
reef tank with lots of diversity using HO or VHO or PC lights, and
what I have and can keep more than satisfies my desires...


-------
I forgot more about ponds and koi than I'll ever know!

I appreciated the comments, but can anyone give me a realistic way to
measure the amount of light necessary for a reef tank based on distance and
wattage or lumens?
There has to be a way, I pressume...


Ruben

kim gross wrote:
Someday you need to learn how to read.

By all means, share *your* opinion, but let's keep the personal attacks
to a minimum.

--Kurt

Tristan wrote:
I'll have to see if he can give me a
condensed version of what he was trying to say.

Please do that. I'm still trying to decide on a system for my tank. I intend to
keep soft corals, with no hard corals, but I don't want to rule out clams either.

George Patterson
Forgive your enemies. But always remember who they are.

RubenD wrote:
I appreciated the comments, but can anyone give me a realistic way to
measure the amount of light necessary for a reef tank based on distance and
wattage or lumens?
There has to be a way, I pressume...


Ruben


Ruben,

There is not a way. For one reason the specific bulbs you run will
effect the light output you get without changing the wattage. A 6500K
iwasaki bulb at 250 watts in JBNY's testing give 605 par. While an
XM15K on the same ARO electronic ballast only produced 171 par. Less
than 1/3 usable light from the same watts.

Lumens will work better but lumens do not take into account if the light
is usable by the corals. You could have a bright red light, with lots of
lumens that would not keep any corals alive since the light would not be
usable by them.

Lighting is one of the most difficult items to decide on for a tank.
The best suggestion that I can give anybody is find tanks that are
similiar to yours with the same corals you want to keep and use there
lighting for a base. Or find people you know you can trust and ask them
for advice. Do not take the advice of any one person as gospel.

Kim

For some info on metal halide bulbs and PAR readings compairing the
amount of usable light check out this web site, it has most 250 watt
bulb/ballast combos listed.

http://www.cnidarianreef.com/lamps.cfm

George Patterson wrote:
Tristan wrote:

I'll have to see if he can give me a
condensed version of what he was trying to say.


Please do that. I'm still trying to decide on a system for my tank. I
intend to keep soft corals, with no hard corals, but I don't want to
rule out clams either.

George Patterson
Forgive your enemies. But always remember who they are.

Wide variation in light need for clams. Derasa's can do just fine under
PC's, while crocea's and maxima's need light comparable to what would be
needed for most sps corals.

On that note, had a baby maxima get ripped up by a blue leg 3 days ago.
****es me off to no end when a 50 cent crab takes out a 50 dollar clam.

Came home from work, and caught the SOB in the act - was on top of the
clam, which was trying to close up, but couldn't because the crab had a
hold of its mantle and was pulling it - I actually witnessed it rip.

Poor clam hung on for 2 days, opening less and retracting its mantle
more and more until it was just shriveled up.

I think the hermits are gonna all come out of that tank - I think I can
just rely on the snails.