Originally Posted by russp
I have both this tank and my cichlid tank on the same timer set for 10 hours and the bulbs are marked as full spectrum. An email to the company got the reply that they were 5000K. The algae I'm getting is a very dark (almost black) algae on the fern leaves and a bright green, stringy algae in the corners of the glass. The ferns are constantly shooting off new leaves and roots and the rotala is developing a lot of new growth at the base of the plants while the tops are looking a little brown.
The black algae on the fern leaves is likely brush algae. This often appears on Java Fern and Anubias if the light is too intense. The very slow-growing leaves attract this algae in light. Some shading with floating plants would help. And I would reduce the duration. Perhaps a second timer for this tank if the other is doing well with the 10 hours.
The "warmer" spectrum of your CFL's should be fine for the Rotala, so I wouldn't mess with that. It is possible the reduction may affect this plant, but you can always change it back. By the way, is any liquid fertilizer being used? This would help the plants use the light more and algae would be less able to increase.
The light reduction (duration) should solve the stringy algae (perhaps hair, or staghorn...) also. It may take some fiddling, you have a higher light and a much lower light requirement plants together, and in a small space it is not always easy to accommodate both.