[quote="Samw"]Enough for what?

I'm pretty sure the 250W would be better. If you use a DO meter to test photosynthesis (oxygen output), I'm almost sure that you would have higher DO with the 250W bulb. In other words, the extra light is not being wasted and is being used for additional photosynthesis. That's the case in my tank anyways which is full of photosynthetic animals.

And it goes without saying that all this depends on what you want to keep. If you aren't keeping anything very light demanding, then the 175W is probably enough.



thanks for the input, but i'm still puzzled as to which way to go, with the se or de for a pendant light setup. j&l recommend a de but indicated they didn't carry many bulbs for them. will getting new bulbs be an issue for the de?
thoughts on remote ballast vs Built in ventilated ballast
thanks
rob

If you look at the graph that you quoted in your first message, you will see that the XM SE produced more light than the XM DE. The same goes with Coravue lamps. The same goes for AB lamps. The same goes with Ushio.

The myth is that DE produces more light than SE bulbs and the data shows it. I'm not the only one saying its a myth. I quoted it from Sanjay's website that you are asking me to look at. The numbers show the SE lamps having higher PPFD. Even your example shows the the SE bulb of the same brand (XM) has higher PPFD.

Here are some random comparisons of same color bulbs from same manufacturers using same ballast. It shows that SE is significantly brighter. I can go on but this is time consuming. The first one is from your own link. It doesn't look like the DE is brighter as you say it is when I look at that same graph. And in most of these graphs, the DE isn't even shielded. Once you shield them (like they normally are), the PPFD goes down even more. So, it looks like for the same brand and color, SE bulbs are brighter than DE bulbs in general with a few exceptions.


http://www.hyperdream.com/~samw/temp/xm20k.JPG

http://www.hyperdream.com/~samw/temp/ab10k.JPG

http://www.hyperdream.com/~samw/temp/ushio10k.JPG

http://www.hyperdream.com/~samw/temp/coralvue10k.JPG[/img]

http://www.hyperdream.com/~samw/temp/sunaq10k.JPG[/img]

thanks Sam, that page wouldn't work for me.

Steve

What are your needs? Do you need to save space? If so, get the DE. If not, get the SE. SE is cheaper. The DE system does have a glass shield so if you are placing the light close to the water surface, you don't need to worry about water splashing on the bulb.

PPFD isn't the same as intensity though, and many of those graphs do tell a tell of increased intensity given off by DE bulbs. PPFD is the most typically used index for photosynthesis because it occupies regions of the action spectrum for chlorophyll. A higher PPFD rating is not the same as saying that a bulb is more intense.

Um I thought we were talking about higher light output all together as in PAR or usable light. why would I care if a light is more intense if its PAR is lower? doesn't make sense. the big selling point of DE's by any store is they make more money selling them. first you spend a lot for the housing 446.00 as apposed for a reflector, socket, cord at 150.00 for a SE bulb and then the replacment bulbs are a higher cost for something that requires less material and manufacturing to produce, so I imagine the profit margin is higher.

Steve

Zooxanthellae use a number of mechanisms not available to plants to harness light energy from other portions of the spectrum. These include, but are not limited to UV-A rays, and are responsible for the rich coloration you see on your corals.

If we were only concerned with the PPFD over the PAR region, then we might be tempted to think that 6500k Iwasakis (189 PPFD @ PAR) are more desirable than 20k Radiums (85 PPFD @ PAR). Try it out for yourself, and you'd find that the corals under the Iwasakis generate xanthophyll pigments to protect themselves from the heat transmitted by higher wavelengths. These give off a rust brown color however, and we tend not to prefer this "look" on our corals. (Though do use lower temperature bulbs on the grounds that the corals receive more PAR light.)

This is why when I argue that DE bulbs generally give off more light, I only speak of raw intensity. Its final effect on coral growth, presentation, or other subjective visual tastes are a completely separate matter to me.

So when you asked us to look at this graph in your first post, what are we looking at here that shows DE gives off more light?

http://www.hyperdream.com/~samw/temp/xm20k.JPG

What are you using to measure intensity? I always thought Iwasakis were more intense which is why growth was faster under them.

So are you saying that Sanjay is wrong when he said "Comparing the data here and other 250W DE articles with the data for 250W Mogul lamps, should provide enough factual information to dispel the myth that 250W DE lamps produce more light output than the 250W single ended mogul lamps."

http://www.advancedaquarist.com/issu...04/reviewb.htm

so one could conclude the coralvue and ushio have the most output?