Gunk from filter lines in tank

Ok, this is the second time it's happened, and I now realize the importance of cleaning those filter tubes.

After my W/C, I turn on the cannister and BOOM gunk just starts flying into my tank. I know what it is, filter tube sediment. What I don't know is how dangerous it is for my fish. Both times I've removed another 10 or so gallons ON TOP OF the original 40% already changed.

There's still some floating around. Is this something to really trip on? It has been filtered after all, right? I checked my water, showed a bit of ammonia, so I hit the tank with a dose of prime and am gonna wait till tomorrow to do another 20% W/C.

Is this stuff deadly?

I hate it. I guess thats why they make the rena tops so easy to remove....makes sense.

Good to know. Common sense says it'd be harmless, but you can never be too sure.

I usually don't turn them off but once a month for maintenance...sometimes tho, seeing as they are plugged into my main power strip, it happens.

I thought about the net thing, but by then it was waaay too late. heh heh