I'm with Ed on this.. 🙂 Don't panic, such a rather harmless Bacterial bloom usualy goes away on it's own again. It can occure if the balance gets disrupted from for example if substrate is disturbed and a food source for the bacteria is released into the water column. It aslo can occure without advance notice. The bacteria can reproduce in vast numbers in an extremely short periode making the water look cloudy. That's why it often reoccures within a few hours after a water change, very frustrating. 🙂 ANd actualy just a guess what the real cause is..
I've had it too a few times in the past with different tanks. Just don't panic and don't get frustrated and wait it out, going on with your regular schedule as always and it balances out again in time. And never used a UV light in my life.
It's he same as the sudden surface skum biofilm, a simmular bacterial bloom but than on the surface.. Same story it can occure any time without advance notice hold on a week or 2 and goes away again.