Needing a bigger tank

[findingnemo1]

Yep you really need to get a new tank. Those tangs will need way more room.
How big do you want and what are looking at spending?

Also you have a cyano problem on that sand. Try siphoning it up regualrily and increase flow in that are and check you nutirent levels. I just finished battling mine and makes a nice tank look so gross