film algae on glass ,,again..

[SantaMonica]

Maroon growth on the screen sounds like cyano, which would mean very weak lights.

[34cygni]

Could be worth your time to read through this thread over at The Planted Tank Forum. As others observed, this may be cyano.

[Vannpytt]

Maroon growth on the screen sounds like cyano, which would mean very weak lights.

Which in terms point out too much C as the parameter to watch. Organic Carbon. Try agressive GAC in a fluidized reactor and (not or) Skimming for a while. This would greatly reduce your dissolved organics relatively fast, along with some large water changes.

I'm quite sure someone has been down the road before, yet I'm not knowledgable enought, but I would speculate this:

With very low nutrients (P & N) in the water, the climate favors bacteria over algae, meaning, the consume will be C instead of P or N. Myself, I have a tank with not measurable either on high precision test kits. <0.2 ppm N and <0.02 ppm P. I got myself a TOC testkit which I'm going to be trying the coming weekend and see how it progresses from cleaning day (little C is extruded as energy into the water) to 5 days when my screens are fully green (lots of C is extruded during the anhydrase).

I'm fairly sure my kit won't detect any difference, as it's far from precise enough, but it's precise enough to monitor buildups over time.

Too much C is also considered a factor (look into the elevated carbon thread on this site) for accelerated bacteria growth, which again, might be killing the stony corals.

Point is: if your scrubber is "too strong", or you are having problems when nutrients are not detectable, your most likely facing problems from another energy source. (C). This is however, as SM states, not algae related.

Edit:

Also, increase feeding to the point where N & P is not limited or reduce the power of your scrubber, relative to the balance between the 3 major energy factors (besides light itself) C & N & P. I would presume there is a balancing point that the scrubber might skew towards N & P being limited, over a bacteria system where C is limited (Biopellets/Zeo). Also, the bacteria cultured from high TOC is also different for the specific type of DOC. (It's different to give bacteria a pen to grow in (a Zeo/Pellets reactor), than to mass release bacteria food (C) and let them grow all over the place)

[SantaMonica]

How much was this TOC test ? The cheapest I found was several thousand dollars.

[new2scrub]

It may be cyano,,,looks like cyano,,,,,but i have NO cyano in display? strange....well I changed bulbs today anyhow. The bulbs I have been using are the 23 watt 27000k ,,, santa should i try the 34 watt bulbs? the 23 watters seemed to work great for the last year....maybe it is because I lost power for 4 full days in the storm last week???

[new2scrub]

o yea: my screen is 16"x9" lit by 2 bulbs on each side with diy coffee can reflectors lined with mylar as the reflective surface I have a 750 gph pump at one foot head for flow and my tank is 55 gallons total volume with 9 small fish and corals. I feed one cube per day and one cube worth of liquid food per day .

[Vannpytt]

If your Glass was fine Prior to that, sure, but it still might be an increase in TOC.

Salifert produces a non precise kit for measuring TOC in the water. It's far from a thousand bucks, and does not measure in ppm, but rather from a sample/dillution test

[SantaMonica]

I was going to try that test, but it was not available in the U.S.

As for his TOC, an increase or decrease in anyone's dissolved or particulate carbon in meaningless by itself. Carbon is not limiting for algae; inorganics are. Carbon is only limiting for bacteria. Think of TOC as the "steak", and Inorganic Nitrate and Inorganic Phosphate as the "smoke". You want the most steak to feed the corals, but you want the least "smoke" which feeds the algae. If you just feed some liquid coral food (which is almost pure DOC), the water's TOC will jump up until the bacteria and corals eat it and bring the levels back down. This eating will produce inorganic waste, which then must be removed by either the algae in your scrubber or on your glass/rocks/sand. The idea is to have a strong enough scrubber that algae grows mostly there and not on your glass/rocks/sand. This will keep most of the "smoke" away (like opening the windows), while allowing the most "steak" for the corals.

High levels of TOC/DOC in the water are better for corals (more steak), although it's very hard to get high levels because the corals and bacterial eat it within minutes. As long as the inorganics (the smoke) are removed fast enough by your scrubber, you can try to put as much TOC/DOC/food into the water as possible. I recent got up to 25 cubes (equivalent) of food per day on my 90 gal, mostly from liquid food, which is 50 percent of what real reefs get. I was reaching the limit of my two scrubbers though, and have since reduced.

As tests have shown, our tanks have yet to get more TOC/DOC than real reefs (although they should have measured mine a few weeks ago). Our high stocking-levels of corals will absorb/eat/consume any TOC/DOC (steak) faster than you can put it in. But you can't keep feeding more and more, because you will reach the limit of your scrubber, and your inorganics (smoke) will start rising.

[Vannpytt]

Are you sure you don't mean POC as that's basically what corals and filter feeders eat, while DOC is what is left and accumulated in the water as there is few organisms bar bacteria who consume DOC? From my sources, POC is a fairly small % of TOC.

[new2scrub]

think I found one of my problems! just got my new test kit in and my magnesium is at 1800+!! magnesium has been shown to kill hair algae off at that level. I am going to do a small waterchange with cheap salt to bring it down...