UV and PAR

[CaverCraig]

High all, I'm new to this forum but have been reefing for a decade or more. I recently stumbled onto a question that no local reefers could answer for me. I have a 250W HQI on my tank and researched it and found that they emit high levels of UV-A and B. Those rays are bad for corals. Now, my HQI has a glass filter on it but glass only filters around30% of incoming UV radiation. I am think of replacing the glass with laminated glass which filters out 99% of UV light. My big question that nobodys been able to answer for me is does laminated glass filter out PAR and if so how much.
Thanks

 

[BigAl07]

Hello and welcome to RS!

 

[Clownfish518]

MH does emit UV, but the glass shield provided with the HQI bulbs filters out enough for the corals in the tank.

SE bulbs use the glass of the bulb to do the filtration.

People have been running these setups for decades without the problems associated with UV burns on corals and fish. This really isn't an issue.

And the glass tops for tanks reduce PAR by about 30%, so I would suspect that what you suggest would have an effect too.

:welcomera

 

[DaveK]

.... Now, my HQI has a glass filter on it but glass only filters around30% of incoming UV radiation. ...

My question for you would be, how do you know that the glass filter is blocking only 30% of the UV?

Most likely the glass is blocking a lot more than that.

If you actually took a measurement of the UV light being produced, and you cam up with only 30%, then you may have an issue.

If your going to replace the glass, you can but the replacement glass must be able to take extreme heat. Normal window plate and similar glass will not, and it will shatter.

Robax "glass" (actually it's a clear ceramic) will block UV and a lot of IR (Infrared light (heat)). This is the material they make "glass" fireplace screens out of. It does have a slight amber tint to it, but this shouldn't be a problem. You can read about it and order it here (offsite) - SCHOTT Applied Energy Systems

However, Robax is extremely expensive. By the time you get it shipped to you, expect to spend about 75 cents to 1 dollar per square inch.

 

[CaverCraig]

MH does emit UV, but the glass shield provided with the HQI bulbs filters out enough for the corals in the tank.

SE bulbs use the glass of the bulb to do the filtration.

People have been running these setups for decades without the problems associated with UV burns on corals and fish. This really isn't an issue.

And the glass tops for tanks reduce PAR by about 30%, so I would suspect that what you suggest would have an effect too.

:welcomera

Thanks for the warm welcomes! What brought this issue up is that my sps corals have seemed to lighten up quite a bit to the point of even bleeching one of my sps corals since the addition of my 250 hqi a year ago. I just changed the bulbs and photo period of my lights to try and help. Previously I was using 1 250W 14000k phoenix with a photo period of 8hrs and 2 3' T5's URI 420nms with a photo period of 10hrs.
I recently switched my T5 420's for T12 454's and changed the period to 12hrs. As for the phoenix 250W 14000k I switched it for a Ushio 10000k and changed its photo period for now to 3hrs a day in hopes of regaining pigmentation. BTW water parameters are on the dot Ca420, DKH 7.6, NO3 0.

 

[CaverCraig]

My question for you would be, how do you know that the glass filter is blocking only 30% of the UV?

Most likely the glass is blocking a lot more than that.

If you actually took a measurement of the UV light being produced, and you cam up with only 30%, then you may have an issue.

If your going to replace the glass, you can but the replacement glass must be able to take extreme heat. Normal window plate and similar glass will not, and it will shatter.

Robax "glass" (actually it's a clear ceramic) will block UV and a lot of IR (Infrared light (heat)). This is the material they make "glass" fireplace screens out of. It does have a slight amber tint to it, but this shouldn't be a problem. You can read about it and order it here (offsite) - SCHOTT Applied Energy Systems

However, Robax is extremely expensive. By the time you get it shipped to you, expect to spend about 75 cents to 1 dollar per square inch.

This link is my source Aquarium Design, Marine Aquariums and Coral Reef Aquarium Tank, Stand, Canopy, and Aquarium Filter System
Thanks Craig

 

[Clownfish518]

Before you added the HQI, how was the system lit?

I do not have much experience with HQI. I ran 150w HQIs on a small anemone tank with Phoenix bulbs, but for the most part I run SE bulbs.

 

[CaverCraig]

Before you added the HQI, how was the system lit?

I do not have much experience with HQI. I ran 150w HQIs on a small anemone tank with Phoenix bulbs, but for the most part I run SE bulbs.

The tank was lit with T5's x4 39W, 2x 10000k and 2x 420nm all uri bulbs.

 

[Clownfish518]

The tank was lit with T5's x4 39W, 2x 10000k and 2x 420nm all uri bulbs.

To go from 4 39w bulbs to a 250w HQI is a huge jump in brightness. What steps to acclimate your corals to the new setup did you follow?

 

[redseareef]

Hi cavercraig,
The glass that came with the fixture will be ample to filter out a majority of the harmful uv rays. Actually, you want some as they do inhibit coloration in some corals.
I would not add different glass, as it will lower PAR numbers. If you are concerned about the new light burning the corals, I would be more concerned about the light intensity change/PAR change numbers. This will bleach out your corals quickly!
Considering what you had, I would start the bulb at least 12 inches above the water surface and run it at about 6 hours a day. Watch corals VERY closely for signs of bleaching.
A good Iodine supplement will help the corals adjust to the excited zoozanthellae in the corals tissues.
We rent a PAR meter at Global Aquarium Supply Homepage for your Salt Water Aquarium needs including AquaC - Reef Complete - Acrylics - Hamilton Lighting - Spectra Pure and I highly recommend one just for the simple fact that you can map the tank out with PAR numbers. This helps with coral placement and makes acclimation much quicker and cuts down greatly on coral loses!
Good luck with it and keep us posted!

 

[DaveK]

This link is my source Aquarium Design, Marine Aquariums and Coral Reef Aquarium Tank, Stand, Canopy, and Aquarium Filter System
Thanks Craig

I believe you have misinterpreted the article. They seem to be referring to the glass that makes up the envelope of the bulb. However, you are using HQI's. Assuming that you mean double ended bulbs, the fixture in use will contain an additional glass filter. Note table 5 and how even "Green" Glass (regular window plate) blocks most of the UV-B, which is the one you need to worry about. The glass used in HQI fixtures will typically block more.

You really don't have an issue with your existing fixture.

 

[BigAl07]

Wow! As noted that's a HUGE jump in the amount of light striking the coral. What's happened and still happening is a "Knee-Jerk" reaction with-in the coral to the light. The symbiotic algae within the coral is literally polutting the coral with over-production of sugars due to increased light. The coral goes into "Survival" mode and releases some of this symbiotic algae. The increase was so great it releases to much and bleaches. I like to see any even remotely big light change (increase in bulbs, type or even just replacing bulb) accompanied with some type of Light Acclimation procedure. Below is the link to how I do it on my tanks (and I've yet to bleach a coral with new lights)
http://www.reefsanctuary.com/forums/equipment/53584-new-light-need-some-help.html#post738647

Now since this has been going on for a year your coral should be "Acclimated" by now but this is also a good procedure for new bulbs. Unfortunately (depending on degree of bleaching and over-all health of the coral to begin with) severe bleaching usually causes the demise of the coral if not corrected quickly.