<a href=showthread.php?s=&postid=10042349#post10042349 target=_blank>Originally posted</a> by TropTrea
an interesting thing I have observed in just about every light study I have seen is that as wattage increases actual effeciency decreases.
However there is another way of looking at it say 2 400W units put out as much "light" as a single 1000W you still might have some advantages with the 1000 watt unit.
1. the single unit will have the light more concentrated in a smller area therefore giving you more penetration.
2. The single unit requires 1/2 the hardware as compared to the two lights would, reducing initial cost by probably around 40%
Dennis
As wattage increases actual light output decreases? I havent seen any such data, got a link or something? Sorry, but I disagree. Look at the PARs on comparable bulbs at various wattage levels... a HQI for example. A 250wattHQI bulb in the same line seems to double in output from 150watts to 250watts, and then again from 250 to 400! Doubling in output for a 60% wattage increase in both cases seems like a good deal to me.
I think the problem that has happened in the past more is that mfg's dont have the same quality bulb at all levels (unless you are Ushio or some company that is larger). This seems to be the problem with most 1000 watters. Their just isnt alot of demand, so their isnt alot of R&D put in. The last data I saw from a mfg of a new 20,000K bulb had the 1000watter pegged at only twice the output of a single 400watter... which is odd, because 20,000Ks seem to get more and more efficient as you go up in wattage, esp at the 400 level... must be all the daylight they put out with the blue that evens the odds. The other problem then is selection... try finding places that sell 1000watters even.
Gotta correct you on this one though...
"1. the single unit will have the light more concentrated in a smller area therefore giving you more penetration."
This is just not true. The system with the greater dispersion wins every time (as long as its built well). Look at a Lumenarc vs a mini-pendant for example. The smaller, more concentrated light source will be brighter near the reflector, but thats it. The more spread out light, in this case, the dual 400's, will penetrate more than the single 1000watter due to better spread. Its counter-intuitive, but its how light works. If you look at how the dispersion fields look, then it makes sense, but in this case, dual 400's will provide better penetration.
I had a 1000 watt setup. The drawbacks are: less dispersion means less spread... as in, more 'beaming' light and shadows. This is great for 'shimmer lines', but using a single 1000watter to light a cube tank will leave most of your corals with a very dark pigmented side, and then a lighter, bleached side from all the shadows. In jnarowe's case, a light mover is the best solution, but still, the dual 400s will produce more usable light... I mean... what corals actually need light that is in the 4000 micrimol range? You would have to raise the reflector up alot, and then you are losing alot of light anyways, where the dual 400s can be closer to the tank. So in the end, the 400s make more 'usable' light. They may have a lower peak up top, but 'who needs it?', and they will penetrate further.
The other problem is availability/cost. Unlike the rationale of getting a 250 instead of a 150 (because the bulbs are $5 more, the ballasts and reflectors cost the same, and there are more 250watt bulbs made), once you get above 400 watts, the bulb selection gets very limited... and components are expensive. A 1000watt HQI ballast cost me about $250... and needs a 220v line to operate. Even a regular probe start ballast is expensive. And then there are the bulbs... $250 isnt uncommon. Heck, I can get two 400s for that much. So their is really very little cost savings, if any.
For another opinion, look at REEFER714's 48x48x24... he started out with a 1000watter, then added a light mover, then switched to dual 400s on a light mover and had more light, etc...
IMO, the only place for 1000watters is with tanks that are over 6' tall, where you need the concentration up top of 1000watt bulbs to reach down into the tank.
