[simon]

Andrew, on May 30 2008, 08:56 PM, said:

I'll go first my current tank dimentions are 66"L x 30"W x 28"D which is 200 gallons before displacement!

My lighting is 2 x 400 watt lumenarc's and 3 x 80 watt t5 so 1040 watts!

No wonder your getting a cube!!
Si

[Social D]

156g Main tank 800 watts of light No actinics yet tho.

If i had my way i would have another 400w over it but its not possible to do damn stairs

[chriss]

Really, what you should have asked is "who's got the most watts per gallon" to get a fair comparison, otherwise lindsay will pop up and say he's got 1200 watts over his sps tank but it's a bit larger than your tank...see what I mean?

Or I guess the other way could be watts per square foot

So, on that basis, you have 1040watts over 200 gallons which is 5.2 watts per gallon or 1040watts over 13.75 sq feet = 75.6 watts per sq ft.

OK, I've got 1020 halides and 85W T5, over mine, 100 gallons or 9 sq feet, so thats 11.5 watts per gallon or 122.77 watts per square foot.

Chris

[chriss]

Tim, on May 30 2008, 08:03 PM, said:

156g Main tank 800 watts of light No actinics yet tho.

If i had my way i would have another 400w over it but its not possible to do damn stairs

Thats 5.1 watts per gallon

[Crabbit]

6x2x2 with a 4x15x18 sump 180G i think. 3x400w with 2x55w blues

[Simon Garratt]

Probably the easyest benchmark to use is Watts/sq meter of surface area...

Accepting the fact that with good quality water the loss of par from surface to bottom in most tanks between 18 and 36" is minimal, there realy isnt a lot in it unless you have an exeptionally deep tank.

Plus you have to factor PAR and K rating into that eqasion..ie 400w of 6.5K will have a substantially greater PAR concentration/sqr Metre, than the equivalant 20K lamp over the same area..

so its not quite as strait forward as it at first appears.

Ultimately, the best way of comparing, would be for everybody to convert thier total wattage (excluding Actinics etc which you would struggle to get PAR readings for) into Watts/sqMtr of surface area, then look up thier lamp PAR output on Sanjays site and then devide each sqM into par concentration /squar meter of surface area..

that way imo you could see 'some' degree of comparison.

So starting off.

800w @ 10K over a 78 x 42 area = 379w/sqm

each lamp has a ppfd index of 120 giving a total of 240ppfd

so the tank has 'in real terms' a usable light feild of 113.7ppfd/sqm of surface area. (not including the 216w of T5 actinics)


even still, like i say, thats a 'very' rough number becouse it doesnt factor in refraction loss or loss of intensity due to angle of incidence which is effected on individual systems by way of reflector efficiency and distance from water surface...

But imo, it would make several differing sysytems more comparable when talking differing lamp types and kelvin ratings.

regards

Si.

[chriss]

Simon Garratt, on May 31 2008, 04:22 AM, said:

800w @ 10K over a 78 x 42 area = 379w/sqm

Are we going to do this the British way and work in sq feet or revert to them there new fangled metric sq meters ?

For those still working with square feet, thats 35.16w/sq ft

If we chuck in the 216W of T5's thats 44.6w/sq ft.

Cold someone post the link to Sanjays site, I can't seem to find it.

Chris

[Tim Parkinson]

here ya go chriss

Sanjay Joshi Reef Lighting Site

he has links to his articles aswell on there, definately one to add to everyones favourites

[Simon Garratt]

Hi Chris.

The reason its done as sqr metres is becouse most research is aquaited back to Fossa and Nilsons research showing average natural daylight intensity at the surface of 1300w/Sqm at 6-6.5K..(thats average without wave amplification)..yes you can do the convertions etc, but to be fair, over half the reefkeeping population have moved over into metric now anyway..(All apart from me who still cant envisage a tank size in Cm.....Only inches )


And like i said, you cant add in the actinic /T5's unless you 'know' what the PPFD output is for that tube. What im saying here is that i could chuck 10,000watts over a 1mtr/sq tank..but it doesnt mean anything unless i know how much of that light is 'usable' light...Thats the real biggy...

Its not the amount of light you have, its a combination of PAR and intensity for surface area thats the key to working out what is and isnt successfull.


Regards

Si.

[chriss]

Thanks Si. And of course, lets not forget the reflector!

[Simon Garratt]

Quite true Chris. becouse although we might have a hypothetical 400W over 1 m/sq.....If we are using something like a luminarc, the spread will be too focused to cover that area evenly unless we mount the reflect a few feet above the water surface to disperse its saturation more evenly over the wider area...(luminarcs do have quite a focused beam)..in essence this means that although we may have a 400W lamp in the middle of that 1m/sq the outside 1/4 of that area might be getting significantlly less light than the centre (although to be fair to Luminarcs they are by far the best for even dispersement across the focal area at this time)..

regards

Si.