new screen and lights dark growth

your picture might be larger than the limit. Best to upload to Photobucket or something like it and then paste the IMG code link.

Are you looking at it under normal light or LED (red) light? Algae will look black under red LED light as it reflects no green component.

I would ratchet up the light but do it only a few hours at a time. So go from 9 hours/day to 11 hours/day for a week and monitor. Since you went to 16 hours/day already, I would at least check it daily to see if you are getting any spot on the screens where the growth is turning white. If so, back it down.

What I would do is pull the screen out every 3 days and rub & rinse in a shallow pan of tank water. This will allow you to remove or thin out the dark growth without causing osmotic shock to the algae (cells burst and partially die). Cleaning under tap water every 7-10 days or so is not so much of a worry as 2-3 times a week, doing so might hinder bounce-back of growth, so intermittent cleanings should be done in saltwater.

 

you don't really need that much. I'm talking about 1 cup of tank water in a pan just big enough to place the screen in and rub it so that the algae rinses away. You won't want to keep that water after you clean the screen I wouldn't think. But I suppose you could.

It doesn't even have to be tank water, it can be just mixed up saltwater to a generally matching salinity kept in a jug. It's not going back in the tank anyways.

 

Take the diffuser off. If you have a base of growth you don't need it. Plus, 80 grit on acrylic is cutting down your light tremendously. Regular diamond diffuser like what is in a ceiling mounted light fixture transmits much more light, so that is likely the main reason for the brown growth.

Also IMO the cool white is not the right LED to have in there - and it's much more intense than 660s at 700mA, it's the wrong spectrum so it's not doing much good, and you will burn a white spot in the screen after removing the diffuser. I would bypass it or replace it with an RB (which will still burn a spot), or better yet a pair of RBs in parallel. Or you can buy one of my 2-chip boards with them pre-mounted in parallel (I haven't started advertising that I have & sell these, but I do)

 

Correct

 

Haven't tried it myself but I recall someone else did and they didn't turn on at 1/3 of 700mA. Maybe wire one of the reds with one blue and the CW with the other blue.

 

Making one of the DRs half power is not going to affect much though. Still a lot of output. In fact my new version has the ability to jumper all LEDs to half power vs full power, including the reds. I did that because I wanted to get rid of the diffuser yet still allow for a low-intensity break-in period

 

How many are you running them now? I think you were at 9 to 11, right? I'd leave it there for a week, see what the growth looks like, then add an hour or two and give it another week, as long as you don't start getting bare spots or white growth, you're good.

 

Wow, phosphates are 5.0 ppm? Really? You need to start GFO, right away. That's where the black growth is coming from, and it's not going to go down fast with a scrubber, you're going to hit nitrate limitation. Start small, a few tablespoons, which will saturate quickly. Change daily to every other day. Test before each swap-out. You want to make a gradual reduction. If you see little headway, double the GFO.

If you don't have a reactor, then you can fill up a fine mesh media bag and drop it in the sump (after RODI rinse) in an area that gets moderate flow. You can use more with this technique because it will have less contact time. Need to get that P down bad!!!