What is that gray-green stuff in my filters?

[Nancy]

Now that my tank is more than a year old, I'm finding I have to rinse out my various filters about one time a month - I don't do them all at once, of course.

But if I rinse out any filter in the water I've removed from the tank, it causes the water to turn dark gray-green. If I leave this water overnight, the very fine gray-green sediment settles on the bottom of the bucket.

Anyone have more insight on what this is? How is it produced in my tank?

Nancy

 

[Colin]

I think that will be the physical waste from Ollie creating that. She's just so much bigger that the larger amounts of solid waste are not getting broken down by the bacteria as quickly... the colour must be reflective of the diet...