New waterfall AS....slow growth

I would run the blue/Violets at half current max, never more. They are very intense, esp the blue. You can run violets full, but only after the screen is mature. Blues photosaturate (too much light), even at half power until maturity.

The crees, are those the 660s or the 630s?

Also try breaking up the photo period into shorter times with 15-30m between. Also 12 hrs/day on a new screen can be too much. Go to 9 at first

 

Hard to do with a mismatch of blue / violet on each, otherwise if they were the same LED you can wire a pair in parallel then put that in the series string and they act like a current divider. That's what I did starting with my Rev 2. So if you swap out the blues for violets, you could do that

Otherwise, placing a small square of diffuser on a panel in front of the LED will help, as will cellophane (Scotch) tape. Don't use dark tape, that will absorb energy and heat up. And make sure whatever you use is not too close to the chip

 

Yes, at least in front of the blue/violet. You only really need it directly in front of the LEDs, even just a 1-2cm square would do.

The diffuser to use is the same stuff that goes in a 2x4 fluorescent light fixture in an office (grid ceiling). Find it in the home improvement store, near the ceiling tiles. Cut it carefully, it shatters easily. I use a box cutter and make multiple passes with light pressure.

 

That looks like the stuff

 

There is a 2MB limit for uploading pics. Try resizing with Irfanview or another photo program. Most allow you to physically resize the picture like from 3000x2000 down to 500x250 or whatever (scale it down) and then it will be smaller and will upload

 

I understand the though process, but when it comes to algae growth, it is such a basic mechanism that it really doesn't seem to matter if you try to match a natural system or not. I've run a photoperiod of 1 on / 1 off continuously and got the same results as if I ran a 12 hour photoperiod. If you were talking about higher life forms like corals and house plants, then I would absolutely agree with you.

In the same respect, the standpoint that we should turn the lights off for a few hours/day, because that is what happens in nature, does not hold water when it comes to growing algae, IMO. I run my scrubber lights 24/7 and get explosive growth. There is no need for a long dark period. It's just that not every system will have enough bioload to support a 24/7 photoperiod of full-strength light; the growth stops, or recedes, leaving one to conclude that they "need a dark period".

One of the things that I incorporated into my scrubbers since June 2015 is dimming. This has resulted in the ability to find a "sweet spot" of intensity for your specific system where you can run 24/7 and not see this growth reversal (which is technically called photosaturation)

I have one customer who is experiencing this exact same issue. He can't grow GHA right in the center no matter what he tries. We tried photoperiod adjustments, intensity adjustments, etc...I wonder if there is a common thread

 

@steve-uk what are your water parameters?
Alk?
Cal?
Mag?
Phosphate?
Nitrate
Potassium?

 

This is typical for a new screen, the flow coverage will even out over time