From reading through many posts here and my experience with this over the last 2 years there seems to be some basic fixes for common algae scrubber problems.
Obviously each tank is different so something working for one setup may not work exactly the same for every setup.
Here is a list of common problems and possible solutions - that I have gathered from reading here.
Algae growth is dark green ---- need to reduce feeding - amount of nutrients is high vs. scrubber area/light/flow. You could also increase scrubber area/ lighting hours/ flow.
Burning or bare areas on screen --- light is concentrated on an area, use diffuser or back light off -- once screen matures it will fill in.
Transparent algae on area of screen --- algae getting too much light in that area vs. other areas. Not bad enough to burn but still washing out. You can live with it or diffuse lighting and/or reduce hours of lighting on ATS.
Black slime on screen - this usually happens in early stages of an ATS - as the screen matures this turns to green turf or hair algae [depends on kind of tank]
NO3 or P not dropping or changing, even when using ATS for some time. Probably other issues in your tank such as accumulated detritus or crud in your sandbed, sump or somewhere.
Ammonia and Nitrite are measureable in your tank..... You need to do something to get the bacterial filtering going. The ATS by itself cannot cycle a tank. Or you have something dead and rotting, -- other tank maintenance still needs to be done.
Algae not growing on screen at all. Check lighting intensity, amount of feeding, and water circulation. Any of the these can be the cause. For a new ATS it may take several weeks for it to get up and running.
Algae blooms, excess growth of hair algae, bubble algae and other nasty algae growing in your Display tank.... Lots of reasons why this can happen. You can battle it by having a strong enough ATS or UAS system, but you need to determine cause and deal with it. The relationship between the hours of lighting in a DT, water chemistry, and the capacity of your ATS are critical here.
You can reduce DT lighting hours - reduce amount of feeding -- increase hours on ATS and/or increase capacity of ATS in some way by increasing hours of light, surface area and circulation [up to a point]
Again, tank maintenance is important here as well.
Some rules of thumb I have found by my own experience.
1. You are always feeding more than you think you are. Size your ATS accordingly.
2. BE PATIENT - do not make changes fast on anything in your tank.
3. A change to your ATS or in your DT will take time to have an impact on your water chemistry.
4. You are not growing algae -- you are using the ATS/UAS as a means to stabilize and control your water chemistry in your tank and have healthy happy fish, corals and other stuff.
The algae growth you get and how much you clean off each time is only an indicator of what is going on.