Sorry to hear about the algae problem! Believe me when I say "I feel your pain" as I'm going through an algae war myself...first the red turf followed by a bad case of cyano.
(thankfully I believe the tide is turning in my favor) I'm sure your in much better shape than me judging by your photos. Your tank still looks great to me!
Sounds like some middle of the night tank watching is in order to find your culprit. I think fish are like dogs and only misbehave when no one is watching, I'd swear mine all look as if saying "it wasn't me!" when I discover an entire colony has disapeared overnight
You sure your flame doesn't want a new home? I think my potter's would like a buddy
