In another thread you said you were hitting algae issues.
In my experience algae in tanks is usually light (like you said), but I think it has more to do with intensity than duration. Don't forget to keep an eye to that also.
Another thing is that algae rises and falls like roman leaders for a while in the new life of an aquarium. So that could also be an issue is that their just a lack of competition at the current time.
Have raised the light and chilled out on the water changes, seems to have slowed things down, hopefully headed in the right direction!