If I were you I'd do water change after water change, you need to get all that gunk out of the water before the tank can return to "normal". You don't want any of it settling out and rotting on the sandbed, possibly suffocating it. I'd do at least 4-5 water changes (or more) and then leave the tank just to recouperate for a couple weeks before you make any major additions. Chances are not only the corals croaked in that tank, some of the sandbed probably died due to less oxygen in the water from the die off/increased temperature. Oh and run some carbon if you have it handy.
