whats growing in my return lines?

[MLconstruction]

Typically i run my return pump at about 40 percent of its potential. Every couple weeks I'll crank it up to 100% to move things around a bit and knock some crud off the rocks. As soon as I turn one of the two ball valves, TONS of crap spews into tank and scares the heck outta all the fish. looks like shredded up paper towel. I believe its some form of bacteria growing in the lines??? It doesnt cause any issues really, just looks gross till it goes into the filter sock. My return lines both exploded last time I cranked it up so all lines are new as of yesterday. Id like to prevent this "growth" if possible. Any tips? Thanks

 

[Fish4Me2]

Are your return lines clear or opaque plastic? I've had the best luck preventing growth with black vinyl return lines. Could you take the approach of putting a sock over the return for the first minute or two you crank up the volume?

 

[kgross]

Not much you can do to limit the growth, without limiting the growth of lots of other stuff in your tank. It is basicly a fact of life with reef tanks. You will have lots of different filter feeding critters growing in the plumbing. It will not hurt anything when you blow it out into the tank though.

Kim