brown stuff in my external filter lines

[devilray]

I have some brown stuff (growing?) in my external canister filter lines. I would like to know what it is. I am hoping this is the "good" bacteria that we all want in our tanks to remove all the nitrates in the water. My nitrate level is <0.02ppm (very good). This stuff is only in the filter lines under the tank (absolutely no light) there is no sign of it in the tank or substrate. Can someone tell me what it is please. Do I need to clean the lines? I am having trouble attaching a picture from my phone. It seems that I need to upload from my computer only. But if you know what I am talking about w/o a picture please help. Thanks in advance!

 

[mfdrookie516]

How are you measuring down to .02ppm? It's just mulm, they all get it. It's not 'beneficial', but it's also not harmful. Some people are OCD and actually use a snake to clean their hoses... I don't.