How often do you replace your MH bulb?

[Bbristow]

I have heard 8 - 12 months. Is this what everyone recommends? I have a reef setup with SPS and other coral. 70watt HQI on an 24gal aquapod. The SPS I have is actually growing well and the bulb is going on almost 2yrs.

[Ping]

Sanjay Joshi, the subject matter expert on lighting in our hobby has said we can go 2 years and longer. It depends on the bulb type and color. Higher K bulbs do not last as long



A cheap no name bulb will not last as long, My opinion - no reference

[Jynxgirl]

I tried to locate that study that Sanjay did but couldnt. It was very intetesting to read. It said something like on average a bulb loses 20% of its ?? (I dont know if it was par) the first year, and then only like 10% the next year. He suggested a system to have your lights so they are not fixed, but to be able to move them down closer to your water as they age.

If anyone has it, can you post the link? Its an interesting read and I would like to be able to again.

[MissT]

I, personally, would reccommend changing your bulbs every 8 months or so. Because you do lose a fair amount of spectrum over time, and as the bulbs get "burned in", they lose a lot of the bluer spectrum first, and you're left with a bulb that is white-yellow in spectrum. Algae LOVE yellow bulbs, and that's why a 6700k bulb is so good at growing macro in refugiums. Going too long without changing bulbs can cause long term algae issues.

[alton]

I have had 250 Watt HQI lamps go bad in 8 months(Down to 50%). I have had 175 Watt Reeflux lamps last 18 months(One at 70% and the other at 95%). I have a light meter and I try to check once a month. Your eyes can not tell when your light goes down hill. But your corals can but normally it is too late.

[Ping]

It is a complicated science. Their are no absolutes, especially with lighting. The difference in ballasts - color temp - quality - etc.

8 mos is a little drastic for a quality MH, I would like to see the data backing that up and the causes. I have only used and read up on SE myself. see below.

http://www.personal.psu.edu/faculty/s/b/sbj4/aquarium/aquarium.html

[tony]

i too am wondering about this, my 12k reeflux is probably just over a year old and ive noticed my algae is growing at a much faster rate now than before with no other changes of note

[envy]

i've heard the same with what a couple of ya'll are saying. you get what you pay for and this has come from many LFS in san antonio. i've heard sps is good for its price range $50-60. this is what i was told from LFS once you go with something like helios, hamilton, etc some times it's pointless to down grade to a cheaper bulb like sps i've been using a 10k hamilton and like how everything has been growing. replacing bulbs can go anywhere from 6-14 months based on brand of bulb and what type of ballest you have. i probably should of left everything above this sentence out allwell thats my 2 cents

[captexas]

I'd love to see the study on the various bulbs. I installed a new Coralvue 14k 250watt HQI bulb at the first of November. 3 months later I am now seeing some strange algae growth and I can only narrow it down to the lighting or the skimmer and my skimmer hasn't changed in those 3 months.

[MissT]

I'm sorry I don't have any hard links for you to follow on the effects of old bulbs on systems, but what I said above is what I've learned from my experience, and that of my customers. While on the topic of bulbs, I came across this layout of 250w SE bulb comparison and, in my case, it proved valuable.

http://www.reefkeeping.com/issues/2007-04/jb/index.php

[RayAllen]

Heres a really cool link with some neet information

http://www.seabay.org/articles/let_there_be_light_3.htm

and this if from another article

How often should I change my bulbs?

Generally speaking, ANY bulb should be changed after 2500 hours of burn time (3000 hours at most). Much after this, the intensity decreases dramatically, and you tend to have a spectral loss at the blue/UV end. Changing bulbs at a regular interval will avoid this. As an example, suppose you are burning your lights 10 hours a day. Assuming 30 days per month, you would want to change the bulbs every 8.5 months at minimum or 10 months at maximum. Do NOT assume that just because a light is bright means that it is still valuable as a light source. This is not always the case. Our eyes are far more sensitive to the red/yellow/orange areas of the spectrum, whereas the greatest loss occurs down at the blue/UV portion (a portion of the spectrum to which ours eyes are not as sensitive. That’s the reason high Kelvin bulbs look dimmer to us).
Over time, as the bulbs dim, your corals become accustomed to the lower spectral intensity. Suddenly, as you change the bulbs, these animals are blasted with higher levels of UV radiation as well as visible light. This is the primary cause of “coral burn” or coral bleaching in captive specimens. In order to avoid this, whenever you install new lighting, or when changing from a lower intensity bulb to a higher intensity bulb, you might want to raise the fixture higher over the tank. Then over a period of a week or two, slowly lower the fixture back to its original height this applies mostly to metal halide lighting as other lighting sources do not seem to produce the same effect). This will give the corals time to adjust to the greater intensity. If raising the lighting is not an option, placing a sheet of glass or UV blocking acrylic between the bulbs and the corals should suffice.

[MissT]

Good info, thanks Ray! Kind of helps explain what I was trying to earlier about spectral changes.

[RayAllen]

No problem Its very interesting information, I especially like the info of the raising and lowing of bulbs when replacing. I know people will adjust height if they change the type of lighting they are using but never thought to adjust when simply getting a new bulb.

[MissT]

It's also pretty effective to take like 3 layers of window screen, put them under the light fixture, leave it for a couple days, remove one, leave that for another two days, then do it one more time. It will slowly acclimate corals to new light intensity, and help keep them from getting shocked.

[envy]

those were some good links

[Bbristow]

Thanks everyone for the reply. It looks like the 9 - 12months win out unless you have your own light meter and can test the spectrum periodically.

Anyone know of a good light meter that won't break the bank?

Thanks again for your posts.

[klondike4001]

Probably a little out of date, but I change my 10k reeflux bulbs every 12 months.

[apedroza]

As a general rule I cange out my bulbs every 10mos, no matter the brand

[MissT]

We just got a Milwaukee Lux Meter, and they retail for around $100. Fun little gadget to keep around