Watts per gallon rule

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

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

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

You simply need to purchase lights made for reef
aquariums, and have a total of 3 to 5 watts per gallon, 3
being on the low side, but good enough for soft corals,
and 5 being where you really want to aim, and 6.6 being great.

People often ask "should I put this coral at the bottom,
or up top". The simple answer is that if you just have
good intense lighting, you don't have to worry about it.

Wayne Sallee
Wayne's Pets



RubenD wrote on 1/4/2007 7:04 PM:
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