good stuff on the pumps. that will get the water going.
ive delt with that algae in the past. i had to get a good hard bristled scrub from a hardware store and go at it. then get a bunch of snails and for sure your tank can handle another tang with all the rock movement they wount be as teritorial. i've noticed that once you can shorten the algae the snails, crabs, urchins, and tangs can better control the diatoms. id test phos and run it through a reactor. +1 on water change and wet skimming. i tank Imo can have a little algae, its just needs to be controlled. its gunna be a pain, but worth it. good luck. nice tank by the way. oh, did you have snails or anything in the tank for algae before the bloom or did you add them after?