250W MH bulbs on a 3ft 65Gal Tank? Can I run them at 150W setting?

[Wally.B]

I have a switchable ballast, and I been using it for years with 2x 150W MH bulbs, on a 4 ft 90 Gal Tank

I recently converted the fixture to with connectors for 250W bulbs, and moved in the bulbs closer together to place over a 3ft 65Gal Tank.

I have a feeling this is too strong since corals appear to be fading and pale/whitish on top side. (All SPS corals, some bought from Frag dealer under 400W bulbs).

Anyone out there running 2x 250W MH over a 3ft tank?

Another question, which I just emailed "Giesmann" support about.
Is it ok to switch down 250W bulbs, to run at 150W, or 175W ballast setting. Since I can convert the fixture back to 150W connectors without a lot a work again.
Sure they run, and are less bright. But are the running properly. (spectrum wise)

Question is will running 250W bulbs at 150W setting shift the spectrum to something bad, and cause me to have algae problems?

 

[redwhiteandblue]

You cannot run the bulbs at a less wattage than what they are rated for. Some may not even fire. If they do work, I would expect seriously shortened life span, and more than likely a large spectrum shift. The shortened lifespan of bulbs would pay for two new reflectors in a year or two. I assume you can't raise the lights up? Perhaps shorten the photoperiod?

 

[Wally.B]

The 250's do run at 175 and at 150. They simply dim when switching the setting month Galaxy ballast. However I will test to see if they fire up from cold, which I never tried so thanks for that thought.

My concern is not about lifespan of bulb.

I will switch back to 150's once I know that is the intensity I want, after a brief trial period.

My concern is about a bad spectrum shift.

 

[stancfii]

Running a MH bulb at more or less than spec wattage will kill the life span. Running a 250w at 150/175 will definitely do so. Plenty of people run dual 250w bulbs on a 65g 3' tank. You can either raise the fixture, put layers of window screen (which you slowly remove over time), or slowly acclimate to just one light and then add in the second. Any of these will help acclimate your corals. You could also go back to running two 150w over the 65, which should be plenty of light for a mixed tank with spa at the top.

 

[Wally.B]

Running a MH bulb at more or less than spec wattage will kill the life span. Running a 250w at 150/175 will definitely do so. Plenty of people run dual 250w bulbs on a 65g 3' tank. You can either raise the fixture, put layers of window screen (which you slowly remove over time), or slowly acclimate to just one light and then add in the second. Any of these will help acclimate your corals. You could also go back to running two 150w over the 65, which should be plenty of light for a mixed tank with spa at the top.

This is a 100% SPS only tank (all new frags)

The reason I changed my bulbs from 150W to 250W is all the frags I was purchasing were under 250W, or 400W bulbs. Was told if I don't have enough lighting, they would lose color, or not grow.

Since this tank is behind a wall, I have no problems raising the hanging light to whatever height I want. THat's the part I'm trying to figure out.

This should explain my frag setup and lighting needs. 250W x 2 for this 3' SPS ONLY 65Gal OK?

How high should I put my lights. I been playing, but currently at 10"

 

[redwhiteandblue]

Keep the 250s, you are fine with those. I have a 250 over a 20 gallon frag tub, 14 awl, 8 inches of water.
and start the light around maybe 14 to 16" and see how it goes

 

[Wally.B]

Keep the 250s, you are fine with those. I have a 250 over a 20 gallon frag tub, 14 awl, 8 inches of water.
and start the light around maybe 14 to 16" and see how it goes

Thanks for that advice. I am running at 10", highest at 12", as low as 8", and kept dropping by photoperiod since I was burning/paling my corals. Was down to 4hrs 30min.

I just raised to 16" and increase photo period to 5hrs. That should be more gentle on corals, but give them enough time in the sun.

I'll work from there.

Should have gotten a proper Par meter from the start.

 

[Wally.B]

So I got an official answer from Giesemann Manufacturer of the 250W Bulb.

Appears there are no issues running a 250W bulb at lower settings.
I believe the bulb will last longer, since you are not pushing it as hard.
My 250W fires at 175W, 150W no problem. To my human eye I see no color change, just a flicker less bright.

See answer below:
-------------------------------------------------------------------------------

Sent: May-22-15 2:41 PM
To:
Subject: FW: WG: Giesemann: Anfrage aus Kontaktformular

Hello Wally,

Yes you can run a 250 watt bulb at a lower wattage setting. The bulb will not burn at its true color rating but at a more blue spectrum. We have been selling the multi wattage ballast for many years now and have not seen a issue with under driving MH lamps. The problems usually come when customers over power the lamps with more wattage than they are capable of handling.

If we can help with anything else let me know.


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