Lighting Question for Rose BTA

[Rig]

what exactly is PAR?

[Ninong]

If you want to use a DIY canopy over a small aquarium, another option to consider would be one of the 150w medium base lamps. These are single end lamps with bases the same size as a regular household light bulb instead of the large mogul base single end lamps that are common in the hobby.

Many people used to use the Iwasaki 150w 6500K medium base lamp before the 150w HQI DE lamps became so popular over here. Then a couple of years ago Iwasaki came out with a new 150w medium base lamp that they called 50,000K (believe it or not!). That new so-called 50,000K lamp has a much broader spectral distribution than the 150w 20,000K HQI DE lamps: http://www.coralreefecosystems.com/l...nical_data.htm

I doubt if Sanjay has ever tested these for PAR because they aren't commonly used in the hobby anymore. Both the 6500K and the 50,000K would be excellent choices for the smaller reef aquarium. Obviously the 6500K would produce more PAR but the color would be closer to daylight. The 50,000K would appear more of an ice blue-white color. It's actually whiter than the 20,000K HQI DE lamps and a comparison of its spectral distribution chart with the BLV 150w 20,000K HQI DE lamp will reveal why that is so. It has always amazed me how the various manufacturers come up with their Kelvin ratings.

Anyway, that's another option that you might want to consider because it would be possible to squeeze something that size into a DIY canopy. The 6500K lamp would benefit from supplementation by a single actinic T5 (or similar), while the 50,000K lamp would be a stand-alone option that would give a nice blue-white appearance but with less total PAR. Maybe we can find some PAR measurements for comparison???

[Rig]

What about a 14k bulb, that seems like it would be a good compromise?

I don't suppoes theres a website where some guy decided to take a buncha pictures of his tank with different light spectrums over it?

Thanks

[Ninong]

what exactly is PAR?

PAR = photosynthetically active radiation. It is measured two different ways but in our hobby it is usually expressed quantitatively as PPFD (photosynthetic photon flux density) with the measurements expressed as microEinsteins per square meter per second rather than the measurements used in the scientific literature which are based on energy and expressed as watts per square meter per second.

The reason you need to know what a lamp's PAR rating is compared to another lamp (both being measured under identical conditions) is because some metal halide lamps produce as much as three times as much PAR as other metal halide lamps of the same wattage.

In the case of the comparison of the two 150w BLV HQI DE lamps, the PPFD measured by Sanjay for the 10,000K lamp was 67 vs. only 28 for the 20,000K lamp. That means that one 10,000K lamp would be more effective than two 20,000K lamps.

[Ninong]

What about a 14k bulb, that seems like it would be a good compromise?

I don't suppoes theres a website where some guy decided to take a buncha pictures of his tank with different light spectrums over it?

Thanks

Some of the 14,000K lamps are bluer than some of the 20,000K lamps. That's because the various manufacturers get to call their lamps whatever they please. Sometimes it's a marketing driven decision rather than a decision based on science.

There are a lot of newer brands on the market now, mostly coming out of China. I'm not all that familiar with those and have no opinion. There was a rush to try the ALS 14,000K lamps three or four years back based on their "beautiful" color but those lamps turned out to have very short lifespans and many suffered from a high rate of infant mortality -- they died within the first two or three months. The U.S. distributor was very accomodating in replacing the failed lamps.

You can find all sorts of threads on the various boards with comparisons of tanks illuminated with various lamps and combinations of lamps. Joe Burger posted a thread once with lots of pics. I'll see if I can find it for you but it won't be of much help to someone trying to light a small 26-gal tank with extremely limited space in the canopy. You are limited to what will fit physically.

P.S. -- Here is Joe's lighting comparison thread: http://reefcentral.com/forums/showth...5&pagenumber=1

[Ninong]

The more I think about your particular dilemma, the more I think that if I were faced with that problem, I would probably choose a single Iwasaki 150w 50,000K medium base lamp and go with that regardless of the other options and regardless of the PAR comparisons -- if we ever find them. IMO that would be a better choice that a couple of PCs, but that's just my opinion and what I would rather have.

P.S. -- People who have seen this 50,000K Iwasaki lamp in person say that it looks closer to a 10,000K lamp with extra blue than it does to anything else.

[Ninong]

I just noticed that that website with the comparisons of the two Iwasaki 150w mogul base lamps does give PAR measurements: http://www.coralreefecosystems.com/l...nical_data.htm It looks like the 6500K is 1.8 times as much PAR as the 50,000K. That's not nearly as bad as the comparison of the two 150w DE HQI lamps where the 10,000K was 2.4 times as much as the 20,000K. That's because this 50,000K lamp has broader distribution than the 20,000K lamp with its single peak in the blue.

BTW, you can't compare PAR numbers from one test against another unless the conditions are identical. Obviously the measurements on the coralreefecosystems.com site were taken much closer to the lamp and without a shield. Sanjay usually places the meter 18" from the lamp and he tells you if the lamp was shielded or not.

[Rig]

Thanks for all the replies Ninong I like the idea of a single 150W 50k. It seems like the most compact way of putting it in a DIY hood would be with one of these, http://www.premiumaquatics.com/Merch...=Pendantshells.

I think there was a typo on the product description for the complete system built with this hood, that I mentioned on an earlier post. This is actually 7.5" wide, so it would be cutting it very close. I think I'll have to wait for my aquafuge to come (hopefully today) so I can see exactly how much room I need to leave in the back for it and the remora.

I'm still a little unclear about what would be wrong with using my existing lighting system. I'd think that I could rip out the unnecessary, keep the fan and the reflector, rivet on a medium based socket, mount an electronic ballast underneath the reflector or off to one side, and have somebody cut me a peice of glass to slide in where an acryllic splash thing currently goes. But maybe i'm envisioning everything being a little smaller than it actually is, or am underestimating the difficulties involved with this plan.

[Ninong]

Thanks for all the replies Ninong I like the idea of a single 150W 50k. It seems like the most compact way of putting it in a DIY hood would be with one of these, http://www.premiumaquatics.com/Merch...=Pendantshells.

You can't put an Iwasaki 150w 50,000K lamp in that fixture because that fixtures holds DE (double end) lamps and the Iwasaki 150w 50,000K lamp is a medium base lamp.

I'm still a little unclear about what would be wrong with using my existing lighting system.

"Wrong" is probably not a good choice of words. Your existing lighting system will work for some animals but not others because it is not intense enough for many of them.

[Rig]

I think theres some confusion.. That pendant is for single ended bulbs I believe, it comes in several different configurations.

I didnt mean to use my existing lighting as is, I meant "work" as in a substitute hood for a mh fixture. i.e., taking out the pcs and retrofitting a medium socket, etc. Instead of building a diy hood.

[Ninong]

I think theres some confusion.. That pendant is for single ended bulbs I believe, it comes in several different configurations.

Oh! I didn't read the copy. I just looked at the picture, which shows a fixture with a double-ended socket.

i.e., taking out the pcs and retrofitting a medium socket, etc. Instead of building a diy hood.

I don't know. Maybe you can do that. I don't know what your present "fixture" that holds the PCs looks like and whether it can stand the concentrated heat of a metal halide lamp.

[Rig]

Well I fiddled with hood forever, its not going to work.


So plan B, mounting the PFO mini pendant inside a DIY hood... How high above the water should the bottom of the pendant be using the 150W 50k. I have AC, and feel that aesthetically the lower the better, so I'm thinking 3.5-4", is that too little? The pendant does not have a fan.

In terms of glare, this is going in the room where people watch tv, so I want to keep it to a minimum. I was thinking about how much the side panels should extend below the bottom of the pendant. Would it be best to have them flush with the bottom of the pendant, have them extend down an inch or, or does this not matter at all in terms of glare and/or the effectiveness of the bulb?

Thanks for all your help.

[Ninong]

Well I fiddled with hood forever, its not going to work.


So plan B, mounting the PFO mini pendant inside a DIY hood... How high above the water should the bottom of the pendant be using the 150W 50k. I have AC, and feel that aesthetically the lower the better, so I'm thinking 3.5-4", is that too little? The pendant does not have a fan.

In terms of glare, this is going in the room where people watch tv, so I want to keep it to a minimum. I was thinking about how much the side panels should extend below the bottom of the pendant. Would it be best to have them flush with the bottom of the pendant, have them extend down an inch or, or does this not matter at all in terms of glare and/or the effectiveness of the bulb?

Thanks for all your help.

The bottom of the fixture should be at least 6"-7" above the water. Light spillover from suspended fixtures can be annoying. That is something to be considered.

[Poseidon]

I agree 6-7 inches is best, otherwise you will heat the tank water to much. You can use black acrylic to block the spillover, or even wood when you build the canopy. Just leave the back open for ventilation, and maybe some slots or something on the sides for air circulation.

[Rig]

The more and more I think about this, the more and more I realize you've all convinced me this is a bad idea. Between lighting problems, nitrates, and the thing taking over the tank, I've decided to pass, feeling all the wiser.

Instead I'll go with my plan B and make an honest attempt to acquire a dwarf golden moray after the tank is established and keep that with a pair of anenome-less ocellaris. Plan C.. A flame hawk and softies. We'll see I guess.

Thanks again to everyone who shared their opinions and advice.