I started my saltwater tank- 55 gallon 4 weeks ago. Added live rock 1 week later (20 lbs.) An additional week later added 2 damsels to help cycle...the following morning my son dumped the entire container of flake food in the tank...cleaned out immediately, water cloudy for 2 days and both fish died. Since then all my chemicals are perfect-near perfect, but I now have this maroon slimy stuff covering everything. What do I do?? Cleaned it off all rock and live sand yesterday and it's already coming back!!