Lighting question

[axelf1]

Hello everybody

I recently built a hang on the back scrubber, its a compact little unit and so lighting is very close to the screen (about 2.5cm or an inch away) Im a noob but have tried to do as much research as possible
My scrubber has been running for about 2 weeks (only started) but im a little concerned since the only algae I can see growing appears to be avoiding the parts of the screen where the bulbs are at there brightest...
algae is growing on the top edge, bottom and sides of the screen but not at all in the centre area where the bulbs are and most of the light is.
I have measured the temperature of the water coming out of the scrubber and its no higher than the input water so its not a heat problem I dont think?

Is it possible the lights been so close makes it too bright/intense for algae to grow ?

Help and advice much appreciated :-)
Dont have a camera to post pictures sorry

[routestomarket]

In a word, Yes!

What lights are you using?

[axelf1]

Hi thanks for the reply, the lights are pl 13 watt 2700k http://www.elightbulbs.com/catalog_product.cfm?source=ShopzillaCSE&prod=TC32014

[routestomarket]

I personally have not used the 2-Pin type of bulb but there could be a few fators that close which are:

heat (remember algae too needs to be kept as cool as the tank)
UV
Light intensity
Light Spectrum

AFIK the colour temperature of a bulb, although designed through the particular gasses and chemicals used, is specified for a normal application.

If the bulbs temperature is 2700 at 6 foot it would be hard to tell the temp etc at 1 "

Hope this helps

[SantaMonica]

The problem is the bulb is to close for the amount of flow. You can reduce the wattage, or reduce the hours it is on (less than 18), or move it farther away, or increase the flow.

[axelf1]

Thanks for the advice guys, because ive already built the scrubber to fit into a limited space and to fit the bulbs I have, the only things I can change right now are the lighting hours and in the not too distant future a new pump for more flow.
Till then I was thinking about trying 3 hours on 1 hour off instead of 18 hours constant light. I could also go for something like 2.5 hours on 1.5 hours off for 15 hours of light. Not sure if this approach is a good idea what do you guys think ?

Thanks again for the help guys :-)

[SantaMonica]

do 2 on, and 2 off, until the growth fills the screen.

[tabwyo]

I wouldn't be too hasty in making any adjustments. It sounds like your scrubber is new new new. Rome wasn't built in a day. Two weeks is too short a time to guage performance. IME, stick with someting for at least 60 days (unless you see serious effects). And when you adjust, wait another 60 days. I may not be running a scrubber yet but I can still say with conviction that the biologic process doesn't appen overnight. If your system isn't suffering, and I mean corals crapping out or fish gasping at the surfce. Unsightly doesn't = unhealthy. Let the scrubber season for a while. Ad when you make changes. Make them for aperiod of time to make sure they don't work. You can't just slap on a ATS and expect wonderful things the next day.

[ChrisD]

Any scope in that precious 25mm cap to include a diffuser over the centre section? I'm guessing (and hoping) that you have some sort of splash guard. if it's acrylic you could just try some fine sandpaper on it to haze it up a bit or even get something from a photographic supplier. they should have 'gels' that are designed to go infront of studio lights so have suitable heat resistance.

Even maybe a bit of tin foil to bounce it back up and about a bit so less direct. You could put a load of pin holes in the foil to let some direct light through.

[axelf1]

Thanks for all the great ideas everyone, really appreciate the great response :D

tabwyo, you are right this scrubber is new new new but I think the complete lack of algae near the lights in this case points to a problem in that area. Also I feel that since its new any changes I make to that part of my system wont have much impact on the rest, rather change it at the start and work towards seeing an even spread of growth on the screen in the early stages or at least an improvement on what I am seeing now... im just not sure that the design is "working" as it is without a bit of fiddling first ;-)

What I have done is change the lighting hours to 2 on and 2 off as suggested by SantaMonica, will leave it alone for 2 weeks to see if there is some sign of algae starting up in the very well lit areas, if theres still a problem, I really like ChrisD's idea of a diffuser and should be able to work something out along those lines

Will post progress as I go, thanks heaps

[axelf1]

Merry Christmas everyone, my scrubber is now working very well !
It seems the extra flow and a 3 hours on 1 hour off lighting schedule has done the trick, did take a long time to grow but its there now and growth is all over the screen.
Will leave everything as it is for now :-)

[SantaMonica]

Yay... so there is the green part of the green and red holiday...