Didn't you have another thread showing a similar white mess on the bottom of your tank?
This "white algae" sure looks like plain ol' fungus growing on uneaten food. Perhaps an uneaten pellet or two, or some particles of frozen food, that landed on the tips of those plastic rosettes and went undetected. I don't know how you feed your fish; do you throw an excess of food so that it scatters all over the tank, and then vacuum up the uneaten waste later? A lot of people seem to do it that way, and that method is asking for trouble...trouble that looks just like this.
What are all those small white dots throughout the water in those pictures?