Determining lighting duration.

Stoke88

I'm starting to get small spots of algae on the glass in my 75g tank. I started out with 12hrs of light a day and have lowered it to 11hrs as of now. I use Flourish Comp as directed on the back twice weekly. Is the 11hrs still to much light daily?

Byron

I would judge the light duration by more than just spot algae. The overall response of the plants, and any increase in algae such as brush algae. The light has to be balanced by available nutrients, and if it is, the plants will use both and algae won't have much chance. The more plants and the more faster-growing plants, the more nutrients are needed and the longer the light duration can be if nutrients are available.

As for green dot algae--the type that appears as pinhead sized dots and takes some serious scraping to remove--this is best handled by cleaning the inside of the glass at every water change even if you don't see any algae. I have ever only seen this algae in my 115g tank, for whatever reason, but I never see it when I run a sponge scraper over the inside of the front glass (and usually the sides too) at the weekly water change.

Byron.