Understanding LED Placement

[CodyRVA]

For all the LED experts out there...

I ran an 80G lagoon reef for several years, amazing coral colonies, growth, color, etc.... using T5s. I got out of the hobby for a few years, came back, committed to going with LEDs.

As someone new to LEDs for reef keeping, my primary questions ->

Do you run your LEDs close to the water, low power, or higher off the water at higher power?

Does a good PAR reading tell the whole story? Can you have good par, but bad lighting?

Context:

I went with a pair of 50W Nicrew Gen 1s over a 35 inch wide 30G tank. The tank is over a year old, chemistry is locked in (testing weekly for ALK, CA, MG, PO4, No3, PH and Salinity), dosing. I've lost probably $100+ in coral, buying $25 frags at a time and at this point I can only assume the light placement is the issue. I have tried a Slimer, Tort, Monti, and Leptastrea (all placed accordingly per lighting and flow requirements). All died largely the same way. The corals will bleach at the tip and then slowly die. They don't brown, they just melt. Some die within 2-3 weeks, others linger for 4-5.

The lights center to center are 15 inches apart. They were about 6 inches off the water. And there's about 4 inches of space between my rock and the water surface, so... 10 inches in total. I was running 20% white and 70% blue. I did rent a par meter from my LFS, the base of the rock shelf was at about 200, water surface was about 450.

In doing a bit more research, I've adjusted the lights to about 9 inches off the water. I turned the power down, cut in half, thinking I would give the tank some recovery time. In my experience too little light will do far less harm than to much. The intent is to buff the lights back up about 10% each week until I get to about 80% blue and ~25% white, but will retest with a par meter.

I do have coralline algae growing on my sump rocks from a cheap LED light running 16 hours per day, rather high off the water, at least 12 inches if not more. However, there's almost zero coralline growing in the main display. I've had several fish die, that routinely would hide in the rock work, eventually develop fin rot and ultimately died from bacterial infection - possibly from excessive light, stress, hiding, etc., but can only speculate.

Chemistry:

Alk: 10 dkh
CA: 425
Mg: 1260
PH: 8
PO4: .04
No3: 1
Salinity: 1.025

 

[mboley]

I would dispute your claim that your chemistry is locked in. Only 1 ppm Nitrate isn't good and your alkalinity is too high. You've said nothing about the flow in your tank. You also have a narrow and I assume shallow tank so the corals can't be too far under the water surface, exacerbating your light intensity issue.

 

[nautical_nathaniel]

Raise your lights, you can see how intense the lighting is directly under them and there is a visible decrease in intensity between the fixtures. You want a blanket of light, not two hot spots.

 

[CodyRVA]

I would dispute your claim that your chemistry is locked in. Only 1 ppm Nitrate isn't good and your alkalinity is too high. You've said nothing about the flow in your tank. You also have a narrow and I assume shallow tank so the corals can't be too far under the water surface, exacerbating your light intensity issue.

Single Tunze 6025 on the left side of the tank (740gph) points across the shelf and slightly up. Return is on the opposite site of the Tunze.

I've run low nitrate with ALK within the 9-11 range before. IME stable ALK is more important than high/low, but by no means not important.

Agreed on the shallow tank, hence my lighting question...

 

[CodyRVA]

Raise your lights, you can see how intense the lighting is directly under them and there is a visible decrease in intensity between the fixtures. You want a blanket of light, not two hot spots.

Thanks @nautical_nathaniel ! This is what I was trying to confirm - blanket vs hot spots. When I did my par testing, the top middle of the tank was very low par, 150ish. Do you think I need to give my tank a few weeks of slowly pushing the power back up, keep it low for a while or push it back up right away?

 

[dwest]

I’ve always increased my LED intensity much slower without issues. Maybe 2% a week while keeping close eye on corals.

 

[Mr. Mojo Rising]

I have a 100 watt nicrew on a 32 gallon tank set at 80%. My 40 gallon has 150 watts. Your par value doesn't make sense to me for the lights you have.

IMO, for an 80 gallon - if it was me - I would go for something in the 200-300 watts range. 100 watts to me is very underpowered for your size tank IMO. Just my 2 cents good luck

 

[CodyRVA]

I’ve always increased my LED intensity much slower without issues. Maybe 2% a week while keeping close eye on corals.

In total transparency... I totally winged these LEDs at first. Bought 2 frags, lost them both, used a par meter, tried again, but had the same result. I think the issue as pointed out above is the lights are creating hot spots and are too low to the surface of the water.

 

[CodyRVA]

I have a 100 watt nicrew on a 32 gallon tank set at 80%. My 40 gallon has 150 watts. Your par value doesn't make sense to me for the lights you have.

IMO, for an 80 gallon - if it was me - I would go for something in the 200-300 watts range. 100 watts to me is very underpowered for your size tank IMO. Just my 2 cents good luck

Sorry for the confusion, this is on my 30G system. The 80G i referred to had T5s.

 

[Mr. Mojo Rising]

That makes more sense lol.

The only other thing that jumps out at me is the several fish dying, that shouldn't happen, and your lights are adequate for your tank but not overpowered so IMO it shouldn't affect the fish in any way.

Both fish and corals dying often points to water issue, not necessarily meaning poor water, but perhaps something fell into the water know what I mean, or chemicals sprayed around your tank. How are your inverts?