scrubber tuning advice please

[Turtle Power]

hi everyone
ive been running a diy waterfall scrubber on my 60 gallon reef setup for some time now but never seem to get green growth or any real hair algae yet nuisance algae persists in display tank ,not a large amount but still there
im somewhat confused why my scrubber wont out compete the dt tank algae as the scrubber is fairly high powered for my bio load ( feeding approx.between 0.5 - 1 cube daily ) and im also running a high end skimmer
the scrubber screen is 4.5" by 4.5" of growing area and is fed by the sump return pipe with flow being at the recommended rate for size of screen ( flow measured at the screen not by the pump rating )
its lit by 4 osram 660nm red leds each side running 700ma
now what im confused by is the growth on the screen always seems dark and a red kinda tint to it ,everything ive read says dark growth needs more light - but if I remove the diffusers that im using for example to increase light it basically burns the algae leaving burnt yellow in the screen holes
so im confused as to if I should be letting the algae grow longer or if what im getting is a dark slime that needs cleaning more often and if so how thoroughly
presently im running the scrubber lights for 15 hours on 9 off - should I increase or decrease lighting period ?
thanks for any help60296030

[Crusinjimbo]

What parameters is your ATS working to address, i.e., NO3 and PO4 specifically? This and structural info such as distance of lights to the screen will help the smart ones address your situation.

[Turtle Power]

hi
lights are approx. 2" from screen
I no longer test for NO3 or PO4 as levels are always very low even on a hanna checker
so im not using the scrubber to lower specific figures but to control tank algae and as there is algae growing in the tank there must be nutrients available despite reading very low figures when I did test as the glass needs cleaning every day - to every over day and some algae growing on plastic surfaces too

[Crusinjimbo]

Maybe the test results are false because your algae growth is extracting the nutes from the water column. It's there somewhere if you are growing on your glass that rapidly. Your screen also appears undersized by the most recent guidance. A one cube per day sized ATS theoretically can handle your feed level but not make much of a dent in starving out the algae level. I went oversized on the screen to deal with my daily feeding and to address my existing nute level. Your screen appears to produce dark algae which usually indicates high nutes, I believe.

[Turtle Power]

yes agreed im sure the test results are false as otherwise there shouldn,t be any algae issues hence I don't test for nitrate or phosphate any more .Im really looking to get the optimal performance I can out of the scrubber at the size it is as I feel it could be more efficient with a bit of fine tuning

[SantaMonica]

Yes needs more light. At least, increase hours to 22.

You could remove the diffusers and sand down the domes on the LEDs a bit by bit.

Also remember that each 50 pounds (23 kg) of nuisance algae covered rock adds one cube a day of feeding.

[Brent1128]

You can see at the bottom where its actually green. That looks to be the part that is submerged in your sump. Maybe you need higher flow since it appears the part thats fully wet is actually green. Then more hours of light. Or take the diffusers off and go for less hours til it quits burning. I would take the diffusers off. Hard to have too much light. Your growth is dark, blast it with as much light as you can first. Then reduce hours til it quits burning. More flow would help it burn less too I think.

Also, I would go with a bigger screen (or 2nd screen). 12sq inches = 1 cube. You dont have enough capacity to filter the food you feed and the nuisance algae in the tank already.

[SantaMonica]

The in-water part is where it's getting the most air/water bubble turbulence.

[Turtle Power]

thanks guys
ive removed the diffusers as advised which dramatically increases the light on the screen and will keep a close eye on it for burning and will try and figure the maximum hours I can keep it on without cooking the screen ,ive no doubt more flow would be a benefit but would require another pump which id like to try and avoid if I can get more algae output from this setup,
I was hoping that once optimized this would be an adequate size scrubber as the skimmer should be taking some of the load ? ( tunze 9410 skimmer )

[SantaMonica]

How much rock do you have, and is it covered in algae?

[Turtle Power]

about 12 - 14kg of rock ,its not covered in green algae, more like some of it looks painted green so to speak and a few areas of longer hair algae ,ill add some pictures , ive had this scrubber running quite a while but it never quite kept up and about six months ago a friend asked me to look after 3 tangs while he upsized his tank which took a lot longer than expected so I had to feed the tank a lot more to keep them happy ,so about a week ago he collected them to go to there new tank and straight after they left algae in my tank increased so they must have been eating it as fast as it appeared and now im left with getting things back on track and removing what must be the built up nutrients from there stay 603260336034

[SantaMonica]

Rock looks good, like natural reef rock with lots of nice periphyton. If you do get the scrubber working well, you might get more growth on the rocks for a while as phosphate comes out.

[Turtle Power]

ok I will see how it goes with diffusers removed and lights on longer and will post an update of results
thanks guys

[Turtle Power]

been a while since I updated ,about a month ago I increased the scrubber size by 50% and also added 4 more leds , so now approx. 5" by 7" screen lit by 6 x 3w leds each side running at 700ma 22hr day on approx. 60 gallon system ,although I had to use a new screen this filled in very quickly as I seeded it using the previous one attached to it for first couple weeks
I would say im getting approx. twice the amount of algae harvest I had before ( will add some pics when I get a chance )
so although the scrubber is much more powerful now and harvesting more the algae in the tank hasn't improved and might be worse ,I understand as santa mentioned built up phosphate coming from the rocks but I also have to clean the glass most days so my question is can the nutrients coming from the rock be high enough to cause algae on the glass also ?
obviously every tank is different but is this a common occurrence and how long has it taken others for there scrubber to clear the display tank ?
( feeding: 1/2 cube a day and also running tunze high power skimmer )

[atoll]

"so my question is can the nutrients coming from the rock be high enough to cause algae on the glass also ?"
In a word yes but the algae you are observing could be diatoms.
Looks familiar?
http://saltaquarium.about.com/cs/algaecontrol/a/aa091100.htm

[Turtle Power]

hi atoll ,thanks for the reply ,I seem to have a mix of allsorts of algae at the moment some of which could be diatoms on the aragonite sand bed but the algae growing on the glass is a green dusting and also some green hair algae on the rocks which seems to have increased since increasing the power of the scrubber , skimmer is still pulling out a decent amount also especially considering how much less im feeding the tank since the tangs left so I guess the nutrients are being purged from the rock slowly ?

[atoll]

hi atoll ,thanks for the reply ,I seem to have a mix of allsorts of algae at the moment some of which could be diatoms on the aragonite sand bed but the algae growing on the glass is a green dusting and also some green hair algae on the rocks which seems to have increased since increasing the power of the scrubber , skimmer is still pulling out a decent amount also especially considering how much less im feeding the tank since the tangs left so I guess the nutrients are being purged from the rock slowly ?

I would guess you are correct regarding nurients coming out of the rock well they have to be coming from somewhere right. They can take quite sometime to get used up by the various algaes so you could be in for a ride with it.

[SantaMonica]

Glass algae is more from fish pee (urea). Rock algae increasing is probably phosphate coming out.