Lighting choices

craigwithasea · 07/07/2007, 08:23 AM

Ok, so I have been looking at lighting setups for my 24L 18H 18W tank for a while now.

This tank will be bare bottom, and I want to keep SPS at all levels (and probably a clam).

I am not too concerned about the tank "looking good" in terms of having a personal preference for a particular spectrum, I would rather provide sufficient intensity for the inhabitants, so I am looking at 10k halides (AB/BLV), in one of the following configurations:

1. 150W DE + 2 x 24W T5
2. 250W DE

My question is, would the 150 + T5 produce sufficient PAR for what I am looking at keeping? Would 250W be overkill? I have read through quite a bit of literature, compared outputs on Sanjay's website, but I guess what I am most unsure about is what PAR level I should actually be aiming for with these types of inhabitants so that I can choose the appropriate option?

Any thoughts welcome.

Thanks.

craigwithasea · 07/07/2007, 08:45 AM

Oh, and can someone tell me if/how Sanjay's PPFD readings correlate with real-world PAR readings? For example, a 250W EVC 20k puts out about 64 PPFD according to Sanjay's site (DE, magnetic, shielded), but there are some measurements of this bulb in the T5 Q/A thread showing PAR readings of around 100-160 on the bottom of an 18" (40 breeder) tank? If anything, I would expect real-world measurements to be lower, what am I missing?

aninjaatemyshoe · 07/07/2007, 03:19 PM

IMO, PAR/PPFD readings are only useful as a method of COMPARING two or more light sources under the same exact conditions. Under different conditions, you will have vastly different readings of PPFD from the same fixture. So there is no "real-world" PAR reading because we are talking about so many variables it is ridiculous. This is perhaps the main reason why bulb manufacturers do not have PAR ratings on their bulbs. What you get from PAR readings is a way of determining between two or more light setups, which one will be more likely to provide more light for my coral in my tank. It is NOT an exact science for our purposes.

Now, on to your first question. Either setup should be adequate in terms of light output/growth for SPS or clams. It is said that 150W MH is about the least intense bulb you would want for the MOST demanding clams/corals (some people will fire back that they've been successful using less, but I emphasize MOST). Since both are adequate, it does come down to color preference.

250W MH only: You will be ok going with the higher color spectrum bulbs like the 20000Ks, which are significantly lower in PAR than the 10000K or 6500K MHs (assuming you like blue). I personally don't care for the washed out look that you get from 20000K or even 14000K bulbs. They basically have one spike at the blue end of the spectrum and little elsewhere. IMO, this drowns out alot of the color you would otherwise see. But, some people don't like the yellow look you get from the 10000Ks or 6500Ks.

150W w/ T5s: The better of the two choices IMO. You will want to use a 10000K or 6500K MH bulb as this will maximize the PAR you get from it. Then you can use T5 blues or actinics to both provide a nice bluer look with a fuller color spectrum than just one 20000K MH. Also, blue T5s produce much higher PAR than blue MHs. This choice most likely will provide even more PAR in your tank than the 250W MH.

aninjaatemyshoe · 07/07/2007, 03:26 PM

"For example, a 250W EVC 20k puts out about 64 PPFD according to Sanjay's site (DE, magnetic, shielded), but there are some measurements of this bulb in the T5 Q/A thread showing PAR readings of around 100-160 on the bottom of an 18" (40 breeder) tank? If anything, I would expect real-world measurements to be lower, what am I missing?"

I might add that in this particular case you are probably dealing with one setup using a reflector while the other not. You would really have to have a complete side-by-side comparison of the two setups to understand what is going on here. But again, these are controlled experimental conditions (or at least they should be). They don't translate into a method of knowing how much PPFD will reach a coral in your tank.

07/07/2007, 08:23 AM	#1
craigwithasea Registered Member Join Date: Mar 2007 Location: Durban, South Africa Posts: 3	Lighting choices Ok, so I have been looking at lighting setups for my 24L 18H 18W tank for a while now. This tank will be bare bottom, and I want to keep SPS at all levels (and probably a clam). I am not too concerned about the tank "looking good" in terms of having a personal preference for a particular spectrum, I would rather provide sufficient intensity for the inhabitants, so I am looking at 10k halides (AB/BLV), in one of the following configurations: 1. 150W DE + 2 x 24W T5 2. 250W DE My question is, would the 150 + T5 produce sufficient PAR for what I am looking at keeping? Would 250W be overkill? I have read through quite a bit of literature, compared outputs on Sanjay's website, but I guess what I am most unsure about is what PAR level I should actually be aiming for with these types of inhabitants so that I can choose the appropriate option? Any thoughts welcome. Thanks.

07/07/2007, 03:19 PM	#3
aninjaatemyshoe Registered Member Join Date: Mar 2006 Location: Dallas, Texas Posts: 2,333	IMO, PAR/PPFD readings are only useful as a method of COMPARING two or more light sources under the same exact conditions. Under different conditions, you will have vastly different readings of PPFD from the same fixture. So there is no "real-world" PAR reading because we are talking about so many variables it is ridiculous. This is perhaps the main reason why bulb manufacturers do not have PAR ratings on their bulbs. What you get from PAR readings is a way of determining between two or more light setups, which one will be more likely to provide more light for my coral in my tank. It is NOT an exact science for our purposes. Now, on to your first question. Either setup should be adequate in terms of light output/growth for SPS or clams. It is said that 150W MH is about the least intense bulb you would want for the MOST demanding clams/corals (some people will fire back that they've been successful using less, but I emphasize MOST). Since both are adequate, it does come down to color preference. 250W MH only: You will be ok going with the higher color spectrum bulbs like the 20000Ks, which are significantly lower in PAR than the 10000K or 6500K MHs (assuming you like blue). I personally don't care for the washed out look that you get from 20000K or even 14000K bulbs. They basically have one spike at the blue end of the spectrum and little elsewhere. IMO, this drowns out alot of the color you would otherwise see. But, some people don't like the yellow look you get from the 10000Ks or 6500Ks. 150W w/ T5s: The better of the two choices IMO. You will want to use a 10000K or 6500K MH bulb as this will maximize the PAR you get from it. Then you can use T5 blues or actinics to both provide a nice bluer look with a fuller color spectrum than just one 20000K MH. Also, blue T5s produce much higher PAR than blue MHs. This choice most likely will provide even more PAR in your tank than the 250W MH. __________________ You are not brought upon this world to "get it"

07/07/2007, 03:26 PM	#4
aninjaatemyshoe Registered Member Join Date: Mar 2006 Location: Dallas, Texas Posts: 2,333	"For example, a 250W EVC 20k puts out about 64 PPFD according to Sanjay's site (DE, magnetic, shielded), but there are some measurements of this bulb in the T5 Q/A thread showing PAR readings of around 100-160 on the bottom of an 18" (40 breeder) tank? If anything, I would expect real-world measurements to be lower, what am I missing?" I might add that in this particular case you are probably dealing with one setup using a reflector while the other not. You would really have to have a complete side-by-side comparison of the two setups to understand what is going on here. But again, these are controlled experimental conditions (or at least they should be). They don't translate into a method of knowing how much PPFD will reach a coral in your tank. __________________ You are not brought upon this world to "get it"

07/07/2007, 08:45 AM	#2
craigwithasea Registered Member Join Date: Mar 2007 Location: Durban, South Africa Posts: 3	Oh, and can someone tell me if/how Sanjay's PPFD readings correlate with real-world PAR readings? For example, a 250W EVC 20k puts out about 64 PPFD according to Sanjay's site (DE, magnetic, shielded), but there are some measurements of this bulb in the T5 Q/A thread showing PAR readings of around 100-160 on the bottom of an 18" (40 breeder) tank? If anything, I would expect real-world measurements to be lower, what am I missing?