Par meter readings
 

I know im going a bit further than most, but out of curiosity i bought a par meter and it arrived today. so i built a holder for it and was playing around with it in my tank this evening.

I dont have really high lighting requirements as i mostly have soft corals. the only sps i have is a green birdsnest and a forest fire monti digi. but i was surprised how low the apogee meter read. middle of my tank which is the top of the rockwork on my 75g read 175 par. the frag shelf where im growing the sps frags are only 100. just under the water at the surface read 450. this is with my LED fixture maxed out. i usually run it a fair bit lower than that (royal blue at 70% neutral white at 90% currently, but higher than that up until a couple weeks ago).

Lately i hadnt had good coralline growth and i noticed that when i lowered my light level to acclimate some frags, when i reached my current level (RB 70%, NW 90%), the coralline growth took off, so i left it where it is. the par measured a bit lower than above readings yet! how are there people that get 500+ par and still get coralline growth?

I recall reading somewhere that PAR meters have a brutal time with LEDs. You are supposed to add like 20% or some such thing? Try googling "PAR meter with LEDs".

At any rate, I know that a PAR reading from LEDs is not the same as a PAR reading from MH.

Apogees website shows that when measuring LEDs the readings get progressively further out the lower you go in spectrum. i believe the chart showed at worst 10% low in the blue spectrum which is admittedly what most of the PAR value is that we get out of LEDs. but 10% doesnt change the numbers that much.

Dont get me wrong, im not about to buy bigger drivers and try and push the readings higher just because they look low. if i max my light out the coralline will start to bleach and i notice some corals starting to close a bit. things just dont seem right, so i go by what my tank tells me.

I wonder what the reading would be under a 400w mh compared to a radion.

Ill try and find some numbers later but I think under a 8 bulb tek light middle of my tank is around 300-350 with old bulbs and it might be in the 450-500 range when new bulbs are in,I think at the surface of the water it's around 1000

I was expecting my measurements to be around those numbers as well considering if I turn up the intensity anymore it seems like everything doesn't like it. Hence the coralline bleaching\not growing, etc. I guess I'm just surprised how low the numbers were.

I always wondered this too, how people are having to lower their lights when they switch from halides to LEDs. My sand bed is blasted with 250 PAR while the upper most part of my rock work gets almost 400 PAR. And I have coral top to bottom. Tank is 20" tall with light 8" off the water surface.

Oh, this is with my 3x250 watt halides running 14K bulbs.

Bringing this back to life abit, I tested my LEDs tonight with a par meter today. Looks like I am getting around 300-500 up top and around 200 on the lower level rock and around 100-150 on various areas of the sand bed. Does that seem about right?

Don't have any lenses on the LEDS currently, but would the lenses help much? I just don't have the lights really high up so I left the lenses off so the light would hopefully spread around even more I was thinking.

Tank is 3 ft long and 2 ft tall