When to replace MH bulbs?

[Mr. Slippery]

How often do you replace your Halide bulbs? For about the last week or so I've been getting a nasty green film on my glass. I've always had it, but could go at least a week before it really starts to be visible. Now, it grows on the front glass daily, and follows the arc of the lights. Towards the outer edge of where the light projects, it's really thick, but towards the inside it doesn't grow. (LMK if you get what I just said ) I have changed nothing, except adding a couple small sps frags. I do a 15 gallon WC every 2 weeks religiously. I use RO/DI, and my TDS reading has always been 2. I am just wondering if the spectrum has changed slightly towards the red end. They are 175x, 10k XM's. They've been running since Aug., for only 6 1/2 hours per day, with no fans for cooling. It just seems funny to me the pattern how the algae is growing.

 

[CamaroJWeed]

Some people say 6 months...

 

[JustDavidP]

I change mine every 6 months or when I find the algae crop outgrowing the SPS

 

[Mr. Slippery]

I'm not noticing any color change/loss in corals, but the algae is gross. Maybe it's time for some new bulbs.

When I install the new bulbs, is there anything special I should do? Will their burn in time affect my corals?

 

[nitrofish]

since we are on the topic of lights, what would you choose for a replacement bulb?

 

[CamaroJWeed]

Radium or Coralvue...JMO

 

[Mr. Slippery]

I like my XM's. I'll go with them again. I like their whiteness.

 

[denvig]

You may want to think about Sun Aquatics.
http://www.sunaquatics.com/index.html
http://www.cnidarianreef.com/lamps.cfm

 

[Chris A.]

Can someone explain what "PAR" is?Don't mean to hijack/

 

[nunofs]

PAR is Photosynthetic-Available Radiation, meaning the amount of the spectrum that can be used for photosynthetis... this way you're comparing only the light intensity that can really be used by the corals, and discarding any intensity that falls outside that range and that might inflate more "pure" output numbers.

Nuno

 

[Chris A.]

Thanks Nuno.

 

[JohnK]

The K rating has a lot to due with the bulbs lifespan. Very roughly, 10k's might be good for a year, 20k's more like 6 - 8 months. Personally I go about a year on my 10k 400's.

IME you won't really see the color shift when you look at the tank, you only see the difference when you put the new bulb in. (I'm just saying you don't really see the shift because you look at the tank everyday).

Lots of things can cause an algae bloom, maybe lights, maybe not. Try to rule out any other factors. Could your RO cartridges need replacement or maybe a fresh DI? (that's the most common cause of my algae problems) I would think that 10k bulbs at 8 months old running 6.5 hrs a day should still have some good life left in them.

jk

 

[Reef55]

those results I have seen before, and still astound me... I have a dual PFO HQI ballast. I currently use XM 10k's. I was thinking of switching to XM 20K's.

Quick math:
Current (XM 10K) = 835 PAR for each bulb (I have 2 of them) = 1670
New (XM 20K) = 314 PAR for each bulb


Hmmm... That means to get the same par under the XM 20K's, I would have to go from my current 2 XM 10k bulbs to 5... READ THAT AGAIN....

For the same PAR, I would have to go from 2 XM 10K's (1670 Total PAR) to...

5 XM 20K's (1570 total par) and STILL have less PAR!!!

AHHH!!! I think I'll stay with my 10k's!

 

[Yaktop]

You may want to think about Sun Aquatics.
http://www.sunaquatics.com/index.html
http://www.cnidarianreef.com/lamps.cfm

haventy tried them myself but heard they were rated good and were cheaper then most. any opinions here?

 

[CamaroJWeed]

Reef55 you are reading that wrong...I have 20K 175's and I get a 1200 on a PAR meter, that is at the waterline 7 inches from the bulb....the sun is ~2000 on a PAR meter on a sunny day for reference...

 

[Reef55]

CamaroJWeed, I read the values straight off the table. How is that incorrect? He (Cnidarianreef) has been doing testing of bulbs for years, and has a setup repeatable way of measuring with industry recognized equipment. The highest par achieved with a 250 watt SE bulb was 950 with an iwasaki 6500K bulb on a PFO HQI ballast. However, he tests without the use of a reflector (actually the bulbs are in a 2'x2' flat black box, but the ratio with a reflector will remain the same).

So yes, with a good reflector, you probably are seeing 1200 PAR. Assuming your bulb is an XM 20K 175 watt, and that the ratio's remain roughly the same at 250 watts to 175 watts, your same setup would produce (835 / 314) * 1200 = 3191 PAR with an XM 10K bulb.

 

[CamaroJWeed]

Mine are coralvues so I don't think they made the test you refered too...if it is the same one from advanced aquarist that I am thinking of...(and you don't sound offensive...) I do have spider reflectors so that could have alot to do with it, But I guess what I meant was that it is not really an apples to apples comparision with a 20K and a 10k bulb, it all depends on the light frequency measured..they could have the exact same PAR reading, just at a different frequencies...but before I say any more let me find my equations to make sure I am stating it the proper way...

Jason

 

[nunofs]

Jason: PAR is used exactly to enable an apples-to-apples comparison, by disregarding frequencies that can't be used by corals. If you look at the output spectrum of a 20K bulb you'll see that it's all concentrated on a peak near 450nm and almost no output to the right of that (the warmer area of the spectrum)... and that's exactly what makes it 20K/blue... a 10K bulb, on the other hand, will have a much more spread out output spectrum, and if you sum the intensity at all those individual frequencies, it's not hard to see that the total value (ie, the PAR) will necessarily be much higher than a blue bulb that only outputs on a tiny range of frequencies... anyway, all of this to say that the difference in numbers quoted by Mark is representative of all 10K vs. 20K comparisons, small differences aside.

Nuno

 

[etszoo]

JMO (I am running 250w de) Growth in my display has dramatically increased under the
XM20K. But I believe there are a lot of factors that could change that. Depth being the
1st. Ran the 10k for about 3mos and the coraline began to whiten on horizontal surfaces. Switched to 20k (about a month now) and coraline and coral growth has exploded. This is just my situation, not saying it is the way it has to be.
I have also read 1yr for 10k and 6-8 months for 20k.
-Eric

 

[JohnK]

coralline often declinces in very bright light (different types thrive in different light levels, when you increase intensity the established coralline may decline, not to say that other types will not begin to thrive) What kind of corals are increasing their growth rates under 20k? IME most corals that require or tolerate high light will grow fastest under lower K light(6500-10k). They will show better color under 20 K but grow slower (repeat, IME, not arguing just offering .02)

jk