Metal Halide Bulb Question

[Kevin S.]

I have a ballast that does 150w, 175w, and 250w. I found running my 250w bulbs was too much for the corals so I reduced it to 175w.

My question is, will this harm the bulb that is supposed to be run at 250w but only getting 175w? It does change the color spectrum to a blue hue, which I like.

Thanks.

[jestep]

Is this an older ballast, also what bulbs are you using? An electronic ballast should not be able to start a bulb rated higher than their nominal wattage. A magnetic ballast, which are rarely used anymore, sometimes can but the color is going to be so far off, who knows what you'll actually get in a tank. I'd imagine the bulb life is going to go down as well. You might get flickering or arcing as the bulb ages even with lower wattage. If the color is blue'r now, it's going to go even further down that spectrum as the bulb ages. Bottom line, is these are nothing like incandescent or even fluorescent bulbs, the bulb is specifically designed for a specific wattage, if you can run one lower the output the outcome over time is going to be a coin toss.

Get some plusrite 20K's if you want something cheap you can mess with wattages on. They typically run $12 and under each. I'm not sure if they come in 175, but they definitely come in 150 and 250. Something you can also do is run the 250's with a lower photo period and use actinic strips to supplement and provide lighting when not using MH. Reefbrite makes some super bright blue and blue/white LED strips. They are a great way to blu-up the spectrum on a tank or to shorten the photo period on a MH fixture.

[Kevin S.]

Thank you Jestep,

I am running 250w 20k plusrite on a Luxecore ballast that is about a year old. I also have 2 80w T5 blue plus bulbs.

I will take your advice and get the 175w plusrite bulbs. Im worried even with a short photo period the 250w will be too much.

[FarmerTy]

How low is the MH fixture on your tank? How deep is your tank? I'm pretty surprised that 250 watts is too much.

Like Jestep says, best to run the correct wattage per bulb and those plusrites are super cheap.

[Kevin S.]

Hey Ty,

They are about 9" above the water and the tank is 20" deep.

It may be a matter of adjusting them to the light. Most of my SPS are 6-8" bellow the top of the water. I did some research and a 175w is enough for 20" deep tank. I just ordered 3 new 175w plusrite 20k bulbs as mine are over a year old. But I did just add T5s.

I have my T5's on from 9:30am to 7pm and the halides on from noon till 5pm.

[FarmerTy]

Seems like a good amount of par and good light schedule. I think acclimation is all you need, its def not too much light for SPS. I have most colonies under 350 par with several at 600 par and no issues.

[Kevin S.]

I would agree that I can run a higher watt bulb, but as it is a mixed reef my acans, zoas and other lower light corals lost a lot of color when I did have 250w bulbs.

[JasReef]

I have a Hamilton electronic ballast for one of my 250W that does the same thing. It can adjust from 125W to 275W. I run it at 250W and never really thought about what it would do if I switched the watts on the 250W bulb.

If I were you I would just raise the light up higher and run the bulb for its rated wattage.