PAR Woes

[jdabs]

So, I'm currently running 2 250W lights in my 135g tank. I'm using magnetic ballasts and SPS 14k bulbs and using some bat wing style reflectors about 12-14 inches off the water. I've been using them for just over a year. MH was new to me with this tank so everything looked brighter than the T5s that I used before in my 45g tank. I thought that I was doing pretty good with my lights. Talking to Robb, I found out he had Simon's PAR meter and he allowed me to borrow it for a night to check my readings just for fun. To my almost disbelief, my readings were incredibly low!!! I'm talking really low!!! At the top of the water level I am getting 70 PAR and it just goes down quickly from there. Even 1 inch from the bulb I was only getting about 400 PAR. I'm somewhat surprised that I'm able to keep any of my corals alive!! :sad:

So, my question is do you think that the bulbs are just getting old and need replacing? I know the reflectors aren't the best, but the reading right next to the lights still wasn't near what it should be so I can't blame the reflectors. What do you guys think?

Robb was kind enough to let me borrow some of his extra 250W bulbs to test and also a 400W ballast and bulb. I'll be working on those tomorrow so I'll post some updates. Unfortunately I won't have the PAR meter to get some readings as I had to get it back to Robb but with PAR that low I would imagine that I'll be able to see a difference just with the naked eye! More to come tomorrow.

 

[jdabs]

Thanks Andy! I'll let you know after I try these that Robb's letting me borrow. What's the typical life span of a MH bulb? Is the SPS (South Pacific Sunlight) bulb just a sub par bulb to begin with? (excuse the pun!)

 

[jdabs]

Thanks Andy! You rock!

 

[rolo65]

That's suprising....I'm running the SPS 14k DE bulbs.....on a small 6"x8"? Reflector.....and I'm getting 1550 right under the glass on the reflector....and 700 2" below water.....and almost 290 on the sand bed....granted I'm running 4 T5s too....but the MH is user the back part of the tank where my sps corals are....my bulb is almost 5 months old at this time....and using a icecap elec ballast.....my light is about 8" off the water....but that shouldn't make the PAR that much lower directly under the light out of the water...maybe the ballast...maybe the bulbs are just old....idk....suprising though

 

[cr500_af]

Unless the bulbs are WAAAAY old, I'd suspect a troublesome ballast/bulb combo or a bad ballast. I'd be shocked if a bulb could be so old as to produce those numbers and still actually fire... though as Rob will tell you, we ran into the same thing on my frag tank. A couple of different 250w bulbs in a Lumenbright reflector made 100 and 150 PAR at the surface, respectively (with the bulb about 10" above the water). Maybe it was age, but I still think it was that the bulbs needed a different ballast to work properly.

Once you get that sorted, I'd be curious to know what you get. I was going to switch from my PFO DE pendants to Radiums... "good" reflectors were not in the budget yet, so I was going to run them in batwings. Tim convinced me to replace my DE bulbs rather than switch yet, saying that I'd get far better PAR that way. In other words, the Radiums (or any other high end bulb) couldn't overcome the cheap reflectors enough to do as well as what I already had. He would have sold me bulbs either way (and did). I replaced my Phoenix 14KKs with Ushio 20KKs, and was pleased with the numbers (750 surface, 300-350 sand, with all the flow "on" so the surface was moderately rippled).

 

[cr500_af]

And John, if you want to test with a different ballast, I am currently borrowing an Icecap from Rob. We should be able to find time to try it with what you have in order to see if the ballast is the problem.

 

[jmaneyapanda]

I agree with Barry. If youre getting only 400 at the bulb through air, either the meter is bad, or the fixture isnt working right.

Whatever you do, phase it it. Dont replace bulbs/ballasts/reflectors and blast the tank for 8 hours. Remember, the animals and corals have acclimated to this weak light, let them adjust upward.

 

[jdabs]

Thanks for your thoughts Barry! I was thinking the same thing about the current bulbs and that they would have to be super old to only put out 400 at the bulb. Today I'm going to try a different 250W bulb that Robb loaned me to see what the difference is. If it's not much then I would like try a different 250W ballast. Robb also gave me a couple of 400W ballasts and a bulb to try. I can't imagine that I would not see a difference with that!!

Jeremy, thanks for the great reminder!! Would you just suggest a shorter light period in the beginning while slowly increasing that light period over a week or two?

 

[jmaneyapanda]

JDabs;533324 wrote: Thanks for your thoughts Barry! I was thinking the same thing about the current bulbs and that they would have to be super old to only put out 400 at the bulb. Today I'm going to try a different 250W bulb that Robb loaned me to see what the difference is. If it's not much then I would like try a different 250W ballast. Robb also gave me a couple of 400W ballasts and a bulb to try. I can't imagine that I would not see a difference with that!!

Jeremy, thanks for the great reminder!! Would you just suggest a shorter light period in the beginning while slowly increasing that light period over a week or two?

Either that, or placing screen material to "filter" the light.

 

[jdabs]

So, I installed the two 250W bulbs that Robb loaned me. With one of the bulbs there is a visible difference in the brightness. Unfortunately without the PAR meter I can't tell how much. The other there is not. Keep in mind these are used bulbs but again not super old. Next, I took the mogul that was on the bulb that didn't have any difference and I added the 400W bulb and ballast. Wow, what a difference! I kind of expected that and boy does it look nice! Amazing what a nice powerful light can do. I ran it for about 2.5 hours and turned it off so I don't bleach upset anything too much. I'll probably run it a little more later today. Also, I'm going to run the bulb that is visibly better on the other 250W ballast that didn't make a difference to see if it was just the bulb or the ballast.

I like the look of the 400W bulbs, but if I moved to 2 400W then I'd probably have to get a chiller or something. N