250W vs. 400W MH Lighting

[Johnsteph10]

Hey!
I haven't written in a while seeing as how everything has been going well.
I have a 120g wide that will house sps, clams, etc. The tank's now been running for 6 months now and am in the process of upgrading the lighting. I currently have 350W (PC/T8s).
My question: Is there really a huge difference between 250 vs. 400? I have heard multiple arguments from each side of the fence. As far as the $ goes, there doesn't seem to be a whole lot of difference (for the equipment or for the bulbs).
I am building a custom hood to mount all this bright stuff in -- I've heard about 10 inches off the water, correct? Also, any rough estimates in how much evaporation is going to occur? (ie: should I have my wife bailing water into the tank all day? ).

I know I've asked a lot of questions -- even a few answers would be great!

Thanks!

 

[taikonaut]

The main difference between 250 and 400 is the amount of electricity it use. The 400W is about 2.5 X brighter than the 250.

The amount of evap. depends on the tank setup. It can be anywhere from less than a gallon in an enclosed setup to a few gallon (~10 gal) in a system with forced evaporative cooling (low humidity, high temnp air, high air circulation). A good estimate is about 3 to 5 gal in most system.

 

[PeeJ]

the 400w is 2.5 times brighter? are you sure? i find that kinda hard to believe. but i really dont know.

 

[PeeJ]

http://www.cnidarianreef.com/lamps.cfm
to me, that does not appear to be 2.5 times brighter

if a 250 watt bulb puts out 600 something par value, then the 400 would be like 1400 par if that was the case.....maybe im reading that wrong but its more on the order of around 50% brighter (comparing two like bulbs with different wattages) with dependancy on balasts on make/model of bulb.

 

[taikonaut]

Sorry, I goof up the math a bit when doing division in my head. The ratio is higher than 400/250 = 1.6 since the higher wattage bulb is more efficient. The ratio should be around 75% or more. It is somewhere on the web, but I don't have the link. Thanx PeeJ.

 

[PeeJ]

not a problem...it just didnt make sense to me when i got to thinkin about it.

 

[ChrisRD]

IMO this is not a question with a simple answer. If you're comparing similar style/model lamps from the same manufacturer, running on the same style ballasts in similar reflectors then obviously 400 watt lamps will provide more light to your corals than 250s.

Unfortunately, there are many other factors that come into play such as styles/models of lamps (for example DE to SE), type of ballasts, reflectors, etc. Once you add that all into the mix I think wattage numbers pretty much go out the window...

 

[PeeJ]

isnt the relationship between power and output the same for lights and sound? i.e. 400 watt light wont be twice as bright as a 200 watt just the same as playing a set of speakers at 1000 watts will not be twice as loud as 500.

correct? similar?

 

[ChrisRD]

Unfortunately, it's not that simple. Different types of lamps have very different efficiencies. In other words, PAR output of a 400 watt Radium 20K lamp might be similar to PAR output of a 250 watt 6.5K Iwasaki.

Also the ballasts driving the lamps can have a very large influence on their output. Output of a 400 watt 10K on an electronic ballast may be similar (or less) than output of a 250 watt 10K lamp on an "HQI" magnetic ballast.

Different lamp styles can have different efficiencies too. In the case of halides for example, a 400 watt Mogul style lamp may not have much more PAR output than a similar 250 watt DE style lamp.

Then there is (probably) the largest factor of all - the reflector. A higher output lamp in a poor reflector may be getting less light to your corals than a lower ouput lamp in a high efficiency reflector.

In other words, if all else is equal, yeah the higher wattage lamp will get more light to your corals. Unfortunately all else is rarely equal!

 

[Johnsteph10]

Wow! Who knew that I would open a can of worms with my questions. Oops!
I've done a fair amount of research about all of this -- and everyone makes very valid points. All of the companies throw around K, PAR, watts, etc. but they don't really take in the whole picture.
Basically, I was wondering about all this since some people have given me parts of 2 250W ballasts without wiring. After sitting down and figuring up the cost of additional parts to get these bad boys working as well as spending the $ for a 3rd ballast and such, the prices weren't all that far from just spending a little more and getting one of those dual or triple ballast retrofit kits.

An interesting tidbit -- I looked back in the archived files and there was a very interesting photo comparison of iwasaki, ushio, sunburst, etc and the differences were fairly substantial.

Keep the comments coming! Let a noobie learn!!!!

 

[ChrisRD]

Some good links you may or may not have already found during your research:

A link to Joe Burger's website. Click on "250 watt metal halide testing" for some great information and comparison pictures...
http://www.cnidarianreef.com/

Here's Sanjay Joshi's website - there are links to articles Sanjay has published with test data on 400 watt and 250 watt halide lamps:
http://www.personal.psu.edu/faculty/s/b/sbj4/aquarium/aquarium.html

Here's Sanjay's article on DE reflectors:
http://www.advancedaquarist.com/issues/july2003/feature.htm

Here's Sanjay's article on Mogul reflectors:
http://www.advancedaquarist.com/issues/mar2003/feature.htm

Here's an article by Richard Harker comparing a 150 DE to a 175 Mogul setup:
http://www.advancedaquarist.com/issues/oct2002/review.htm

 

[-JB]

Unless you are running radium or other blue MH. The difference is pretty minor. The 250 watt MH Ushio puts out almost the same PAR as the 400 watt Ushio ~20% difference. The AB lamp about ~15%.

 

[hsosa]

Im currently running one 250watt Iwasaki with a Ice cap ballast. I purchase about two yrs ago. Im glad I spent the money for this set-up . Now Im planning on adding an additional light since my upgraded tank is 300gallon . I was planning on buying a 400watt Blueline ballast and running a 20k XM bulb which ive been reading good things about anyone using these XM bulbs? Championship lighting has the blueline ballast on backorder and Im kinda debating now if I should just get a 400watt Icecap ballast which willl essentially run any bulb. I know I need more light but my tank mostly has softies and dont plan on keeping sps anytime soon. I figurare I can upgrade as I go. I already building the canopy. eventually I wiill run 4mh bulbs and two 96watt 03 acttinics PC . I would definately spend the extra cash to get a good set-up .