Mason, this is the 250w iwasaki vs. the 400w radium. For the record, the 400w radium at 12" had a PAR of 343.09 , not the 500 I originally thought.

Wow, that's sure different from the results JB got with the 250W. He did his measurements at 8" not 12" but I would not have thought it would make such a difference. On the HQI ballast he measured a PAR of 403 for the 250W Radium.

There is a lot of difference based on distance and whether it is in water or not. Variables aside, I think we can pull from this the fact that a 250w Iwasaki is at least 50% more intense, PAR wise, than a 400w Radium.

So if you are swapping the more intense 250 for the less intense 400, you should take precautions to safeguard your corals! Agreed?

That's exactly what I was thinking. Although I didn't expect (but not surprised) that there would be up to a 50% difference between the two setups.

Thanks again Brad!

I am assuming that this is good news for me, as I was starting to worry a bit about putting 2 400w Radiums on my primarily softies/LPS reef. :confused:

I think that would be fine Em

Brad, any thoughts on PAR value of a 10,000k Iwasaki 400w vs a 10,000 Iwasaki 250w? and how about Par value of a 250w 10,000k SA? And finally, what about Par Value on a 6500k 250w Iwasaki.

Thanks Doug

I don't recall iwasaki making 10k, so no thoughts there. I also don't think about SA bulbs or 65k Iwasakis, so nada again. Steve might have thoughts on it though. :razz:
Pretty much I don't think about PAR at all. I think my Ushio 10k are pretty and bright, same for my Radiums, but with more blue. I saw some info I knew was wrong in this thread and thought I should post what little I knew to help protect some corals from bleaching. That's all.

But Steve is gonna love this thread and I'm sure he'll answer all the questions above!! :biggrin:

oh where to start.. first if you are buying a system 400 watt rqadiums are a waist of time (unless you already have the ballast and don't want to change them.) radiums are a German bulb style which we all so commenly call HQI. the 400 watt bulbs had a starter added for the north american market but as Brad said they only put out 380ish PAR with a distance of 12" and 1/2 of that water. that would probably coralate to about 500ish by JB's test methods. the same ballast pushing 400 watt ushio bulbs on Brads tank put out 450ish PAR, on the same token the 250 watt radium pumped out over 550PAR on the same set up (6"air and 6" water) compared to the 380ish of the 400 watt.. now they both were run on a HQI ballast but sence we all know there is no such thing as a 400 watt HQI ballast the 400 watt was never driven to its full potential (and never will be unless someone figures outhow to make a german reactor ballast work in Canada :mrgreen: )

as for Iwasakis, yes they have a high PAR but they will not beat a 250 watt HQI ballast with a bulb like a radium or an AB on the ballast they are made for.

A good AB bulb on a 250 watt HQI ballast puts out around the same PAR as a 400 watt Iwasaki (mine was higher than 2 of the 4 I tested, the same as 1 and a little lower than the other)

now there were all kinds of factors to play with as I was doing thoes tests in different tanks so the turbidity could have been different as well as others.

(if anyone has 250 watt bulbs they arn't using at the moment and would be willing to lend them to me for PAR testing just msg me, I would like to test more than just the SA bulbs compared against a 2 year old AB (I already know the AB will have more PAR even at two years old, but I would like to see how they compare against other bulbs)

I don't have a regular 250 watt ballast but I am looking at getting 1 ballast of each type (if I can get them for cheep enuf) and setting it up in the garage so I can test any bulb. I am going to rig it up so all I have to do is use switches to select the ballast that will power a single test socket.

now as for the original question, I don't like any of the mentioned methods of aclimitating to new lights. I have three main reasons

1, moving the lights higher is not practicle for 80% of reefers,

2, using screens can be diffacult because if you get PVC ones they melt and the metal ones rust. Also you have to find a way to hold them in place,

and 3, shortening up the lighting period doesent work and usaly results in bleached corals.

what i recomend (and was recomended to me by Eric B) is to get a good timer and set your light cycles to turn on for 1 hour then off for one hour, then on for 1 hour and then off for one hour ect.. for the full 10 or 12 hours you would normaly run your lights. Do this for 2 or 3 days and change the times to on= 1hour 15 min off = 45min, a few days of this and then on = 1.5 hour off = 30 min, few days more then on = 1 hour 45 min off = 15 min. do 2 days of this then go to normal on for full cycle.

the reason this works is that a coral can handle 1 hour of intense light no problem befor it will reach it saturation point, then by turning the lights off for 1 hour its levels go down and it will be ready for the next blast. as this goes on the coral also develops protection from the more intense light so when you bump up the time on it will be able to handle it.

now I don't know the fancy terms of what kind of saturation level the coral will reach after 1 hour but I think i am getting a basic explanation accross.

Ok now Doug, this is the second time some one mentioned a 10000K iwasaki was that a typeo? just incase it wasn't I did a serch and didn't find any referance to Iwasaki making a 10000K bulb so to answer your question any of the other bulbs you mentioned are going to be higher PAR than a SA 10000K 250 watt.

Appeper, Joe's test was pretty good, i actualy injoied it but it has one serious flaw, it is through air only. why is this a problem you ask.. well think for a minuit air has no substance ad nothing to slow the light down or deminish its intensity other than distance its self, when i do my tests I try to do it in a situation that it would actualy be used in. i do it at a distance of 12" and I try to get 1/2 of that to be through water. the reason for this is that water affects different wave lengths differently, some colors it slows down more than others which can have little or maybe a dramatic effect on the PAR level of a bulb. it depends on which combanation of wave lengths they use to make 10000K. when I set up my test bench in the garage I am going to increase my testing distance to 24" (18" water aqnd 6" air) this will show actual penatration power even better.

Steve

Steve, if you can manage it, and if your meters will read it, might I suggest you try to test the difference between still surface water and water with ripples? I've read where the water ripples can magnify the light reaching lower levels up to 15 times, in a pulse-like effect.

Mitch