AeroCloner.. Filled with algae

So Last night I checked my cloner and it was fine. Woke up late today and found algae all over my aero-cloner. On the inner walls, On the roof piece (where the plugs sit), everything is totally green. I tore it down and washed it all out.

But what could have caused that? And how could it happen so quickly?? Anyone? All I'm using is Cloning Liquid from Cloneex. (Not the gel, just the stuff you add to your water.)

Clean well with h2o2 (my preference ) or bleach.
Use non PH'd tap water,no hormones, make sure you have no light leaks.
Good luck

Light is getting in. Make sure you use opaque plastic.