I have been somewhat negligent in not cleaning out the external filter on my aquarium for a long time. It is very overrated for the tank though, so probably didn’t threaten the health of the fish.
The external filter consists of a large round canister with a pump in the head, and many thick filters stacked in the base. Water is drawn in at the bottom, through the filters and pumped out to a sprinkler bar from the top of head unit. I should have splitter valves at the top and bottom of the pipes running between the filter and the tank, but have not got enough of the right kind of valves so have to plumb them directly to the filter. This makes it tricky to remove the filter. I have a tap at the top of the two tubes running from the tank, so with them in the off position the pipes do not run free when I remove them from the filter BUT the bottom connection of the filter does of course want to empty the filter of the head of water it contains, so I have disconnect the pipes and move it to a bucket very quickly.
Cleaning was quick and easy.
I had been running the external filter in tandem with the original internal filter for some months. The sprinkler bar was located outside the filter bed for the internal filter and made a lot of noise and agitated the water a lot. I decided it was time to stop using the internal filter and just use the external filter. I decided to fit the external filter’s spray bar to empty into the internal filter’s filter tray (with a reduced number of filters). The original spray bar fitted on top of the filter pump centrally but the external filter fitted its spray bar at one end. I was unable to connect the external filter to the internal filter’s spray bar, so I had to cut a notch in the side of the internal filter’s filter tray to allow the pipe for the spray bar to come in from the side rather than from behind (or underneath) as the pipe would have kinked. I had to protect the pipe as it run over the rough edges of the notch I had cut crudely.
All seems to have worked. Fish seem happy and fed the moment I added food to the tank.
We shall see if all is well in a few days.