Help - my whole tank is gone?

Last Sunday I did a total clean up of my tank. I had been working overtime a lot and didn't do my regular maintenance. I have had this tank for over five years with no problems. A couple of days after I cleaned my tank my fish started dying. there is now a white cottony film - fungus I presume over everything. I only have two fish alive - a cardinal tetra and a neon dwarf rainbow. What did I do that caused this and how do I fix it before starting over again.