A Tale of Filter Abuse.

How long will a canister filter continue to run if you don’t clean it? Perhaps surprisingly, the answer could be as long as three years – but don’t try this at home!

So, how do I know the answer to the above question? I’m sorry to say that it wasn’t a result of some long-standing controlled experiment. No, it was a simple case of neglect and it is not a story that I am recalling from my early days of fish keeping. This just happened and I have been keeping fish for over 20 years!

The filter in question is an Eheim 2126 canister filter, which is an excellent filter. I have previously referred to it as the Rolls Royce of canister filters. It has a built-in heater with remote control and temperature gauge. It has a quiet motor and a solid build quality. It has an excellent quick-disconnect system that makes it easy to disconnect the filter from the tank for maintenance – so I have no excuse for neglecting this great piece of equipment!
The filter has been installed on my 75-gallon planted tank for several years. Despite having had as many as 22 aquariums at one time, I currently only have this 75-gallon tank – so I haven’t been overworked trying to maintain lots of tanks. I keep a notebook in which I make notes whenever I clean the tank, clean the filter, add new fish or plants, etc. – so I can’t say that I didn’t know when the filter was last cleaned.

I have been conducting regular water changes on the 75-gallon tank – at least once every two weeks and sometimes more frequently. The tank is heavily stocked with live plants but lightly stocked with fish. It has a Coralife light hood with four 96-watt compact fluorescent light bulbs. The tank also has a CO2 system that injects the CO2 into a reactor on the output side of the filter. The CO2 is absorbed into the water by the time it enters the tank from the filter. The tank has been entered into the Fry-Angle Home Show every year and has even won Best Aquarium in 2008. I think it is an attractive aquarium with healthy inhabitants but I recently realized that something was wrong.

I was sitting at my computer when I heard an odd bubbling noise coming from the tank. On inspection, it turned out that the filter was not running. The bubbling noise was caused by a build up of CO2 that was being pumped into the reactor, escaping into the tank via the filter output tube. But why wasn’t the filter working? Once I removed it from the tank and opened it up I got the answer. The filter was so full of a sludge-like build up that the filter could no longer pull water through it and either the motor head or the impeller had ceased to work. How did I allow the filter to get into this state?

As I mentioned before, I keep records of work done on the tank so I checked back through my notebook to see when I last cleaned the filter. I was shocked! The filter hadn’t been cleaned in almost three years! I know that canister filters can easily run for 3-6 months between cleaning, depending on the load in the tank. I guess that type of reliability resulted in me not worrying about the filter on a weekly or monthly basis. Unfortunately, those weeks and months ran into years without any attention being paid to the filter.

If the motor was blown, I’d have to buy a new filter – a costly replacement considering the local retail price of $380 (another reason they might be considered the Rolls Royce of filters). I decided to take the filter head down to Noah’s Ark in the hope that a replacement impeller would do the trick. Great news! Noah’s Ark not only had an impeller in stock but Stephen kindly allowed me to test the impeller in the filter head before purchasing it. When I plugged the filter head in at the shop the new impeller sprung to life. I figured I’d dodged a bullet and was really singing the praises of the Eheim filter. How could it possibly put up with the abuse I’d handed it and still keep ticking with nothing more than a $40 replacement impeller? The short answer is – it couldn’t.

I got the filter home, cleaned it out and reassembled it with the new impeller. The filter worked! But there were several power cuts at my home that weekend and every time the power went out, the filter refused to start back up until I removed the head, cleaned around the impeller and reassembled it. Furthermore, there was a minor leak coming from somewhere on the filter. After not removing and cleaning the filter for almost three years, I couldn’t be removing it every time the power cut out or every time I unplugged it to do a water change. I realized that the filter head had also been damaged by the neglect so off I trundled to Noah’s Ark to dig deep and buy a replacement filter.

It never occurred to me to purchase anything but a straight replacement Eheim 2126. If it could last three years without being cleaned, how long could it last with proper maintenance? The new filter has been installed and the tank is running perfectly. I’m suitably embarrassed that I could have allowed the filter to run so long without cleaning it but I figured that it was a lesson worth sharing through Fish Tales.

I was lucky not to lose my fish due to the amount of sludge in the filter slowing down and finally ‘killing’ the motor. Having a lightly stocked tank with lots of live plants obviously helped. A tank with a heavy fish load and no plants to help clean the water would have probably met with disaster long before the filter actually stopped working. So, please don’t try this at home. Learn from my mistake and ensure that you keep your filters on a regular maintenance schedule.

And if you are looking for a quality filter – I strongly recommend the Eheim 2126 canister.