Yeah I had one of the downsides of canister filters happen today. I showed up at the fish room about 4 pm only to find no flow through my 2 magnum 350s. Well I have no idea how long they weren't running so I had to clean them out and change the mechanical media and when I turned it back on I tested the water and had to do a fin level water change. Luckily I have a sponge in there so the cycle will recover quickly