High phosphates huh? Did you double check with another test kit first? Most phosphate test kits are useless because if you have any your algea is using it all up. If you are feeding flake at all stop and rinse any frozen foods in ro/di before feeding, these are both contributors to high phosphates. For the cyano like stuff did you try putting some more flow on it and cut down the light for two or three days, put a sheet or something over the tank and don't let it get any light at all, then do a large water change the day after.
I'm glad you got rid of a couple tangs just keep in mind your clown, naso, and unicorn all grow way too large for that size tank, I've read more than a few stories of people with 300+ gallon eight foot tanks giving them up because they seem cramped, they need a lot of room to swim around. Stick to ones that stay under 10 inches max size. Plenty of other fish in the sea to add. Also maybe post some pics of the weird algea to be identified.