[Canadian]

I apologize in advance for the odd timing of these posts. I had intended to post after work but got caught up with the realtor and was running around all night until going to bed. Now I'm awake in the middle of the night so I thought I'd do something "productive"

First I think you are being overly critical of my light fixture. I would not call it low quality but about a middle of the road one. Sunlight Supply makes good fixtures and these were not much different then the first generation Tek fixtures in terms of lighting output. Slightly better reflectors and active cooling would improve it somewhat but how much do you think that would be? 10%? 20%?

Nope. It's low end. For comparison here is a picture with PAR values for a higher quality T5 fixture. Keep in mind the setup here is still far from ideal given that the fixture doesn't extend the length of tank so keep your eye on the PAR values in the middle of the tank. In this picture you're seeing similar PAR values to your LED fixture with newer lamps and better quality fixture.

Secondly, while the bulbs were old, the only references I could fine say that T5s lose about 10% output over 2 years. The problem for reef tanks is the shift in colour which can lead to undesirable algae etc. But let's say that the degradation was 20% for the sake of argument. So my 300 PAR with the T5s could mean 375 PAR with new bulbs. Still much less than 500 PAR with the LEDs higher above the tank then the T5s were.

Here are PAR values on that same tank one month after the above. This hobbyist measured 20-30% PAR drop WITH ACTIVE COOLING over the course of 6 months. After driving up the fan voltage he was able to cool the fixture enough to keep the drop to 10% over 6 months. So again, old lamps on a low quality fixture (without active cooling) will show 30% + PAR drop over the course of 15 months.

Argue all you want but however you set up my test, new bulbs or not etc. my LEDs handily outperform my T5s. That's all I am claiming.

No arguing. Just trying to ensure there's a reasonable comparison without making hugely inaccurate leaps in assumptions. As shown above, your PAR values are hardly representative of a good T5 setup. And while you claim the comparison is only to your T5s you're trying to report the values as if they're some how representative of T5s by commenting on the relative quality of your fixture and expected drop in PAR of T5 lamps.

Dr. Joshi is an engineer and has been testing all sorts of lights, especially MH, for a long time so I would consider him a good independent reviewer. Here's also a more recent review of a top of the line LED fixture, the AquaIllumination:

http://www.advancedaquarist.com/2007...searchterm=PAR

This one clearly shoes the AI unit outperforming a 250W MH unit. Granted, the MH ballast used may not be top of the line but is probably typical of one used by many people.

I'm well aware of the article. It is quite dated. And again, the comparison is to a 250W 20,000K bulb on a crappy Coralife ballast with an uknown "polished aluminum parabolic reflector". At least you're recognizing that the parameters of the comparison aren't exactly even here.

With respect to who has the biggest PAR; really, who cares. Stoney corals appear to photosaturate between 400 and 500 PAR so having 700 or 1000 PAR is probably pointless other than for bragging rights. I doubt it will do the corals much good.

FWIW, I agree. This was only commented on because Steve got involved in the conversation and has, in the past, made a big deal about the high PAR values he got with his DIY MH setups on his SPS tanks when comparisons to T5s were made. Now that LED PAR values in a typical setup (such as yours) seem to be similar to those of "good" quality T5 setups (see pictures above) he seems to be suggesting those PAR values are now acceptable.

As for longevity and degradation of LEDS, that is fairly well established. While high powered LEDs are fairly new to our hobby they have been around for a decade and are well tested. Low power LEDs have been around far longer then that so the degradation of LEDs is well understood.

With respect to PAR? Please show me the data.