What is this growth?

[daftwazzock]

Left my tank for 10 days during it's cycling while I went on holiday. Came back to a fuge overflowing with chaeto, salt creep starting to mess up my atk, but what really blew my mind was this growth and bubbles on the bottom. Can someone identify please?

 

[DSC reef]

Looks like a mixture of diatoms and cyano, common in new tanks. Siphon out next water change.