Tank has been up and running since last Nov, and then last week all of a sudden green algae is popping up on the glass any idea why?[/QUOT
You could be over feeding or your lights are stating on for too long.
That's what happened to me
Check the type of tube you used for your new T5. Make sure it is not a 5000k which is for plants and algae loves it.I just added t5 lights so not sure if that did it or not