Why is 175 watt MH so popular and not 250w?

[toefu]

I noticed that after viewing many many reef tank webpages, that the 175 watt MH setup seems to be much more popular than the 250 w setups.

 

Here's what i don't understand:

 

- the 250w seems much cheaper to setup, and the bulb is typically cheaper or same price as the 175w.

 

- more power?!?

 

- The 250 watt DIY just seems way too simple.

 

 

and also, I plan on setting up 2x250w MH 20k XM bulbs on an M58 ballast over a 55 gallon, is there a reason why not too many people seem to be using the m58 ballast? They are relatively cheap ($20 on ebay) and the bulbs are not that costly either.

[MrConclusion]

This is a perfectly FANTASTIC question. The only reasons I can figure out are:

 

(a) Many LFS and online stores stock only 175 watt lights, and 250's, 400's are special order. Not only do you have to wait longer, but the "special order" thing makes people think, "hey these must be pretty unusual and I don't need that!"

 

( There is a "rule of thumb" out there (which is as patently false as the watts-per-gallon rule of thumb) that 175's are for 24" deep tanks, 250's are for 36" deep tanks, and 400's are for 48" deep tanks. Who the hell has a 48" deep tank!?!?!?

 

This is obviously wrong, because one of the finest acropora farms in the country is near me, and I have seen how they use 400-watt lights suspended less than 10 inches above the surface, and the corals are less than a foot below the surface. check out www.drmaccorals.com

 

The depth penetration of a lamp depends almost entirely on the design of the reflector, not the power of the bulb.

 

© There is a belief that the bigger bulbs are going to jack up your electric bill (consider that baking in your oven uses over 5000 watts, and your electric hot water heater uses at least 3600 watts) Plus, the bulbs and fixtures are going to cost a little more, and the LFS doesn't want to alienate the customer (possible lose the sale) by pushing even more expensive hardware.

 

(d) Because the human eye has an amazing ability to adjust to different light levels, people can't really percieve the brightness difference between a 175, 250, or 400 watt unless they are running right next to each other, in similar fixtures with similar reflectors.

 

How many times have I been talking to someone at the LFS and asked them "Oh, you have MH lights - what wattage are the bulbs?" and they say, "I don't know... they're really bright... kind of like that one over there" and they point to the closest demo. Seriously, I have been in retail for a long time and the average person has no idea what they're buying or what they should be buying.

 

But 250's and 400's are a better deal if your application requires them. As you step up, the bulbs are more efficient. In other words, the larger the bulb, the more lumens per watt. Also, more lumens per dollar. 400's are three times brighter than 175's, but the bulbs never cost three times as much.

[jdsabin1]

If you look over at ReefCentral.com you'll see that the 250's are damn near ALWAYS recommended over the 175's for the reasons Mr. Conclusion stated. My guess is that if you're putting halides over a nano however, they are smaller tanks and simply don't require 250 or 400 watts when 175's will do. That was why I put two 175's over my 20. Fact was, I didn't need anything more than that.

 

'Nano Logic' applies here.

 

*shrug*

[wetworx101]

About efficiency, I recently stumbled across an article that documented the lumens output by 175watt, 250, and 400watt Halides. It was speculated, that due to ballast design, 250watt bulbs were the most efficient, with 400watters only putting out slightly more than 250s! So 250s seem the way to go for now.

[Jahkaya]

Heat would be a Major factor as well. When Trying to replicate the Sun you can never have too much wattage. If you had a chiller for your 10 gallon and had a 1000 watt pendant(and alot of money to spare) I would say gor for it. The main concern at that point would be of course heat, but also acclimation. Most Coral from LFS would not be accustomed to such light and would get a major "sunburn" and possibly die. I intended to put a 250 over my 18H, but determined that I did not want a heat issue and it was not needed for the Type of animals I was to have. Though, I may have faster growth with a 250 I opted for a 175 so that I could mount it in a canopy and not boil my tank. Some people do not like the look of pendants, but in JDsabini's Case I love it. My wife, on the other hand, is not too keen on it. even though you will have more reflective surface in a smaller tank I still feel that a 175 is still a 175 no matter what tank you place it on. It makes no difference if the corals are placed the same distance from the light.

[Jahkaya]

Wetworx:

 

Wasn't that comparing 250 HQI's to 400 Mogul, Though? I think I read the same thing.

 

I would love to see the 400 HQI's in action.

[wetworx101]

No, I think it was just single ended...wish I could find it as well.

[foo]

That thread of RC jdsabin1 was referring to:

http://reefcentral.com/forums/showthread.p...threadid=201570

Packed with lots of technical information if you get off on that sort of thing. It's a long read but worth it if you're trying to make a buying decision for MH in 175W, 250W or 400W.

They seem to be saying 250W MH HQI driven by an IceCap is the all around winner (best price/performance ratio).

[markjd]

I think it's probably a nano thing. It's not the standard to find nano's with 250w or bigger MH's over them. However, as you can see from this board, there are a few nano tanks with 250w lamps or more over them.

 

As for cost, it turns out that the replacement lamp cost of doing a Radium blue 250w SE on my 20G is less than a Radium blue 150w DE What's even funnier, is that the Radium blue 400w SE is about the same price as the Radium blue 250w SE! By the way, these are going by the local Australian prices of Radium lamps. I don't know about the US prices.

 

As I am in the building stage of my 75G, I figured I may as well purchase a Radium blue 250w for my 20G. That way, I can just add the 250w to my 75G when I finally get that up and running.

[Kirklan]

I don't beleive this has been addressed but the M58 ballast MAY not start up the bulbs required for aquarium MH lighting. Look up the difference between probe start and pulse start bulbs. Also M58 magnetic ballasts are less effecient and run a lot hotter than electric ballasts. Here is some infor copied from Hellolights.com

 

"Q. What is the difference between a "probe start" and "pulse start" ballast?

A. Without getting technical, a "pulse start" ballast has an ignitor which helps start the lamp, while the "probe start" does not have an ignitor. Most ballasts sold in MH fixtures here in the U.S. are "probe start" (ANSI: M57, M58 or M59)."

[EJ7B18C1]

Originally posted by Kirklan

I don't beleive this has been addressed but the M58 ballast MAY not start up the bulbs required for aquarium MH lighting. Look up the difference between probe start and pulse start bulbs. Also M58 magnetic ballasts are less effecient and run a lot hotter than electric ballasts. Here is some infor copied from Hellolights.com

 

*IMHO* that's an overstatement. The M58's will start up most MH bulbs EXCEPT Radiums. I have had many 250W bulbs in my day and all but the Radiums fires on the M58 ballasts. Reason being is because the Radiums don't have an Ignitor inside the bulb for the M58 to fire it. Thus the Radiums need a *Pulse Start* ballast which has a Ignitor with the ballast. Other then that you can buy any bulb for a M58 250W ballast if the bulb itself has a built in Ignitor to have it fire on this ballast.