I have 3 400 watt MH lights and I was wondering how often I should change them (every 6 months, once a year, etc.)? I keep mostly soft corals and a few anenomes. Thanks.

they say around 9-12 months. I usually change mine around 11 or 12, then again it all depends if I can see a noticeable difference in how the corals look as well as the color of the light.

12 months seems to be the norm, but studies (ok study) shows that you can run them for 18 months before a significant drop in PAR.

I like that 12 month idea. Easy to remember!

I wouldn't go anymore than 12 months.

Not all metal halides are created equal... :-)

Bulb life varies depending on brand, the particular bulb you get, your photo period.

I thought the ARC had a PAR meter they rented out. That is the best way to tell when the bulbs need replacing, imo.

I think we do but I saw it at the last meeting and I think it is being passed around right now.

Not all metal halides are created equal... :-)

Bulb life varies depending on brand, the particular bulb you get, your photo period.

I thought the ARC had a PAR meter they rented out. That is the best way to tell when the bulbs need replacing, imo.

I approve! +1

The life of the bulb is dependent on the brand/style/color/etc. The only real accurate meausre is PAR output (as far as the corals care). If you keep a photo log of your tanks (with the same camera settings every time) then you will be able to have a visual reference to color shift.

I thought the ARC had a PAR meter they rented out.

Yup, we sure do! Its a $10 rental fee (with credit card number on file, or deposit).
It is currently rented out but should have it back within the next few days.

yeah, i need to rent that thing sometime..!

One other thing, w/ the PAR meter, if your water is yellow, that can effect your par readings, so keep that water clean! ;)

If we are getting out of generalities and into specifics read this series of articles:

http://www.personal.psu.edu/sbj4/aquarium/articles/MetalHalideLamps3.htm

I would also add the ballast you use should be considered as well. A spectrum shift does not necessarily mean you should change the bulb either.

I would say 12 months is a fair number, but you can change more often if you like. It is a hot topic to be sure, but ultimately it seems the adaptive nature of corals allows them to do fine for quite a while under MHs especially since the spectrum shift is slow.

Ballast will play a huge role. Electronic, Magnetic, or HQI. Bulbs will run longer on some with less color shift and loss in PAR and get "used up" faster on some other types of ballasts. HQI runs the bulbs "hotter" and typically you get more light/PAR out of this ballast-bulb combo but you have to replace the bulbs more frequently. It depends on what you are looking for: Max output or longer bulb life or maybe a compromise of some of each...
:)

Man don't go more than 9 months...I pushed the envelope and I can really see I should have replaced them at least 2 months prior....I am going to go to 6 month schedule now.

yes, I have that cool lil par thingy thing thing.....man my HQI went down in PAR. Time to replace, and its only been about 8 or 9 months.

If I have to move to 6 month MH changes, I will switch to T5s in a heartbeat.

I agree with Cameron that would be rediculous unless you have a lot of couch change.

wow you have to pay to rent the par meter? My Chatt club lets us use it free... :tongue:

/d

wow you have to pay to rent the par meter? My Chatt club lets us use it free... :tongue:I don't think anyone is making any money on the deal so I don't have a problem paying to use expensive equipment.

For how much this club does for us I don't mind paying for things like that at all.

I didn't say anything about you guys minding or you guys gettin ripped off... Don't be so touchy. ;) I just said we are able to use it free, then again we only have like 24 active members heheh... I think it would be pretty tough to do that with 400 members more than half of which you prob don't hardly know.

/d

Yeah I was just saying... I wasn't taking offense to it at all. Yup that would be REALLY hard with this many people. We would need a tracking device on it.

I didn't say anything about you guys minding or you guys gettin ripped off... Don't be so touchy. ;) I just said we are able to use it free, then again we only have like 24 active members heheh... I think it would be pretty tough to do that with 400 members more than half of which you prob don't hardly know. Not touchy either. I was just pointing out that even though we pay it all goes to a good place.

stop being touchy about being touchy.... heheh

/d

Tsunami- what size tank? 3 X 400 watts for softies and anemones is a lot of light. You PAR shift may not be as critical as for those that are keeping ultra-light animals, such as SPS, clams, etc.

Agreed to the point that bulbs, ballasts, etc will make a difference. Even things like ventiliation on the bulbs will make a difference.

The rental fee is to help pay for the par meter that was purchase in July.

Rob

As long as your corals are growing why wast the money. I replace my 150 and 250 HQI every 18-24 months