Common Name: Bacterial Mulm, Saltwater Mulm, Mulm or Detritus
Scientific Name: N/A
Bacterial Mulm is usually noticed after tank maintenance or after handling or changing aquarium parts. It is a residue found on the inner pipework of a saltwater setup and in low flow areas. It is often described as medium to small light colored gel-like flakes floating around in the display tank. Most often than not, these light colored gel-like flakes are a result of a sudden rush of water in the return line pealing the layer of buildup on the piping inner wall and pushing it along with the rush of water to the display tank. This also happens in the other(sump) direction but less noticeable as sumps are mostly hidden in saltwater setups. It is not pretty, but it is also not harmful and can be dealt with quite easily by manually removing it from the water column and some future hose maintenance.
Mulm build up on vinyl and silicone tubing is very common and any aquarist that introduces these lines to his/hers system should consider adding tube cleaning to the maintenance schedule. A simple cleaning solution of disassembling the tube and bending it with hot water inside or hot water+viniger mix will displace the buildup and help to slush it out. A tube cleaning brushes can be used to remove the residue as well if it is resisting the bending solution.
Tube with a light coat of buildup on the inner walls and a piece of mulm caught floating in the display tank:
Common Opinion: USE WITH CAUTION