Lighting MH advice.

[Young Frankenstein]

Just my opinion after much research on the subject :
For tanks 50 gal and over use only 400 watt MH, reson for this is the smaller the bulb the less life it has and is more expensive to by compared to watts per $ . Example most 175watt are rated for 6000 hrs of use, most 400w are rated for 8000 hrs, 1000 watts are rated for 12000 hrs etc.
So 2x175 watt will cost an average of $ 160 for 6000 hrs, 1-400w will cost $ 110 for 8000 hrs. The money you are saving will go towards the extra 50 watts of electricity use + you will save some $.

For fish tanks in the 90-150 gallon range where some people may use 250 watts, I would get the 400w and have a less of time cycle with the MH, where I would leave the actinics on longer.

for 150-250 gal I would use 3-400
Mongul base also helps with the life of the bulb.

 

[ReefWreak]

Both are interesting ideas for sure.

for tanks 50g and over using 400w, I think that's a bit skewed. The issues with that are that 400w will be a TON of light on the tank, and especially with a reflector that maximized your efficiency, you're going to have a LOT of corals that are uncomfortable or don't show true colors because it's so much light.

As far as the rated lifespan of these bulbs, I don't know anyone who has let an MH bulb run until it burned out. Most people change their bulbs once every 3 to 24 months, depending on their budget and what they believe is best for their corals. There is a great article in ReefKeeper magazine that was really helpful for me to learn about the lifetime of halie bulbs, which also made me now a believer of keeping your bulbs for 2-3 years.

The article showed the PAR dropoff measured over a period, where the biggest dropoff was in the first 3 months, and then the dropoff rate was much smaller for the next 2 year or so period of time.

There is also the idea of the color shifting of halide bulbs as they age to consider. Some people may not like the colors that they shift to, as they'll shift from the higher kelvin degree end of the spectrum to the lower end of the spectrum (i.e. A 14k bulb may shift to 10k over it's life, a 20k may shift to 16k over it's life, etc).

The problem is that while we've got some great sources from Sanjay and others about the colors and PAR of bulbs, ballasts, reflectors, the problem is that noone really does longitudinal studies of bulbs, other than this one that I referenced before: http://reefkeeping.com/issues/2007-04/ac/index.php

Anyway, you've got some interesting concepts, though I wouldn't necessarily endorse them. They are based on semi-solid reasoning, I don't think they're practical though, since no one burns their bulbs to the life of the bulb.

 

[Young Frankenstein]

ReefReack thanks for the response. I haven't been able to keep 175 for more than 8 months. Nothing is written in "stone" ex. if heat builds up and theres no adequate ventilation it will significantly reduce the life of any bulb.

Perhaps we need some input from other people posting the wattages of their bulbs and the time they change them.

 

[ReefWreak]

You mean they burnt out? I've never even seen a halide burn out. I've used 10k bulbs before and run them well over a year. I used the original coralvue bulbs that came with my lighting setup when I bought it used that were said to have been run for a year, and then I ran them for another year after that.