It is occasionally necessary to disassemble your aquarium filter, dump out excess sludge accumulation (a little bit is good, that’s your friendly bacteria), clean the motor, that kind of thing. Do keep in mind that there is sludge is not only in the filter, but also in the filter hoses, especially the intake hose. And that water runs downhill.
If you’ve already sprayed your living room carpet with sludge once, don’t assume that was all the sludge in the hose. This also applies after spraying sludge around twice.
I should have quit after sliming the carpet the third time. Instead I reassembled the filter. Apparently I installed the outlet at too high an angle, because when I turned the thing on, it sprayed me in the face. Just because you dislodged the sludge in the intake hose, doesn’t mean there’s none left in the outlet hose.
All of this is especially less fun if you’re doing it at 1AM.