Slimy thing in the sump

[mehmet]

LHi! My sump is covered with this slimy substance, and when touched slightly, it breaks apart and goes into the aquarium, sticking to the corals. How can I clean this? What is it? Could you help me?

 

[Dan_P]

LHi! My sump is covered with this slimy substance, and when touched slightly, it breaks apart and goes into the aquarium, sticking to the corals. How can I clean this? What is it? Could you help me?

Movie did not play on my iPad

 

[unclejed]

LHi! My sump is covered with this slimy substance, and when touched slightly, it breaks apart and goes into the aquarium, sticking to the corals. How can I clean this? What is it? Could you help me?

Turn off return pump to aquarium and then siphon out the gunk.