Black film covering chaeto

[reefer1]

I run a chaeto reactor in my reef tank. It uses a red/blue LED strip wrapped around the outside of a two little fishies reactor.
Lately, I’ve noticed a black film growing in the reactor and around chaeto. The chaeto grows quickly and I remove as much of the film with about 30% of the chaeto each week. I also wipe down the film off the inside of the reactor.
Any idea about what’s going on?

 

[lion king]

That's another form of algae, likely what most call hair algae, the red/blue spectrum feeds the growth of that type of algae. If you are still having positive results, the lowering of nutrients, not the growth rate of the chaeto. Results should be measured by the lowering of nitrates and phosphates. At least it's not in your dt. right. If it bothers you or you are not getting the results you want; you could switch out your lights to a warm white spectrum, which works better for me.