Diatom Growth after switching lights

[sinkingbeach]

Is it normal for diatom growth after switching lights from 440vho to 500w halides. I switched them several days ago and have been adding an hour more halide period daily(5hrs. today), the growth just started today.

Thanks
Francis

 

[sinkingbeach]

My temp has also gone up 2 degrees from 78 to 80 over this day.

 

[bertoni]

I have seen algal growth spikes after such lighting changes, so I wouldn't worry too much yet. It might settle back on its own. If not, the usual approaches to algae problems might help.