Help! Red Sea Valve Erratic!

[flfrosty]

Tank (Reefer 200 G2+) has been running for about a month, no problems, quiet, etc.

I come back from running an errand and all the flow to the sump is going through the overflow pipe.

All fish and inverts are accounted for. Opened the valve a bit to resolve the issue. Struggling to get it back to equilibrium.

What is happening?

 

[flfrosty]

I think I solved the mystery...one fish is missing...RIP Mr. Neon Goby