Par recommendation?

[jda]

It is true. PAR is not equal in the different kinds of light. There is more useful radiation in MH than in most T5 than in nearly all LED. PAR mostly measures the visible spectrum from 400 to 680nm, or so, when coral can use 350-850nm. Most LEDs are made to pop the meter in this spectrum, but recently, there have been some more efforts to add UV and IR to LEDs, which will not register on a PAR meter. ...so if you have 350 PAR with a LED then you probably captured most of the radiation that it is going to emit for a coral to use, but you can bet there is a lot more light coming from a T5 and LED since they have spectrum that the PAR meter cannot capture.

LEDs need to be kept lower because of some kind of harmful radiation either through lenses or more likely through some peaks that are too high. Like I said above, 350 is about as high as I would go on a LED for most corals, but the same corals would thrive under 3x that amount from a T5 or MH unit... it is not quantity, but quality.

Have you seen Tullio Del Aquila's MACNA talk "The Facts of Light?" It is really good and just facts. He really goes into efficiency (there is none) and how spectrum really matters, including what we cannot see. It is really good, IMO:

 

[Bpb]

Par is definitely not equal among all light sources as you guys have discussed. The “a photon is a photon” argument doesn’t work perfectly.

@jda and others recently helped advise me in my transition from t5ho to metal halides. I was concerned I would be torching my corals with the sudden jump in par and they assured me I’d be fine.

In the 3 weeeks since switching my overall par has increased roughly 2.5-3x what it was under my t5ho. I experienced zero bleaching or retraction or anything, including “low light loving” lps. I actually experienced a sudden growth spurt and needed to drop my reactor ph and increase the effluent simultaneously to make up for growth. A couple larger acros have grown well over 1/2” in just 3 weeks time.

I don’t think it’s just a matter of horsepower nor do I understand why. But it just must be the specific blend of wavelengths that are received well without any bleaching, despite a dramatic increase in intensity.

 

[b4tn]

A lot of great info. Somehow notifications where turned off for me on this post so I missed the bulk of the conversation lol. But that was a big question I had but figured I was dumb for thinking it. If Par is equal between LED, halides, T5's? I always thought why would I cook my corals with LED's but see all these people with tons of light from halides doing fine. I guess that make sense. But I got my first round of measurements. I am using 2 Ocean Revive lights 12" above the surface that ramp 3 hours up and 3 hours down. Blue spectrum is on for 12 hours including 6 hours ramp and white is on for 10 hours including 6 hours of ramp. Max intensity right now is 25/85

A couple things I found interesting. I had always thought the light crossing under the center brace would be the most intense part of the tank. This is not true the brace creates a pretty big dead spot as you can actually see from the coraline on the back. The Green acro center tank is getting 108 par I had thought this was one of the highest light points in my tank. It has always colored up but is very slow growing, now I know why. The Acro far right is normally vibrant lime green. I had a nitrate spike that turned it brown and its getting its color back, but its growth pattern makes total sense. You can see its obviously growing towards the center where the light is much more intense. Pretty much all along the back wall lingers in the low 100's. I am thinking I will be getting some magnetic frag plugs and moving my leptos to the back wall. The pink blotch at 124 par is a very sloooow growing monti. Now I know why it grows so slow The blue coral on the plug on the back wall at 97 is a miami chalice so that should be a perfect spot for it. last the SPS on the left hand upper rock are Red planet, slimer, pocilipora (which seems to thrive anywhere I put it), and a monti on the frag rack you can see all sit in the mid 200's and seem to be happy. They encrust and show PE.

 

[b4tn]

I forgot to add, these numbers are modified. I have a ton of surface movement. So when measuring the numbers bounced all over the place. If the meter read 210, 220, 230 I would pick the number that popped up the most normally the middle one so 220 * 1.08 = 237. The 1.08 is the immersion modifier for the sensor I am using.