I have a 5 gal that has a built in filter. It has always worked fine but it's stopped working properly the other day out of nowhere, the water just dribbles out. It happened during a water change, when the water level dropped it couldn't suck up water, but then when I filled it up it worked like normal then half and hour later it was dribbling. I've checked the filter box and nothing is blocking it, I switched it off at the wall and turned it back on, it went like normal but then next time I came back to check the water was barely flowing again. I tried switching it off and back on again but it hasn't worked again.
"No human being, however great or powerful ,was ever so free as a fish"