External filter flow rate has dropped, what to do?
1. Replace the fine filtration pad in the filter.
2. Check if the filter media is packed correctly, especially fine-pored media such as activated carbon. Media can become compacted, making it harder for the filter to pump water.
3. Check the rubber O-rings on the taps. Some models have two sets of taps: regular screw-on taps and quick-disconnect ones. The sealing rings there usually begin to sag, and water starts leaking into the filter head, eventually leaking out elsewhere, though it initially seems to come from under the head. For repair, it might be enough to remove the rings and lubricate them with petroleum jelly (Vaseline) or find similar ones at a hardware store.
4. If a spray bar is installed at the outlet of the external filter, check the outlet holes; they may become overgrown with algae, causing the water pressure to drop.
5. Clean the filter hoses.
6. Disassemble the filter head, inspect the impeller and the impeller chamber, and clean and rinse them.
External filter is leaking, what to do?
1. Disassemble the filter and lubricate all rubber joints with petroleum jelly, wipe off excess petroleum jelly with a napkin. Petroleum jelly is non-toxic and will not harm your fish. It is recommended to regularly check and lubricate rubber joints with petroleum jelly.
2. Over time, water may leak from under the hoses where they connect to the taps. Disconnect the hose, cut off 2 cm, and reattach the hoses.
3. Check the rubber O-rings on the taps. Some models have two sets of taps: regular screw-on taps and quick-disconnect ones. The sealing rings there usually begin to sag, and water starts leaking into the filter head, eventually leaking out elsewhere, though it initially seems to come from under the head. For repair, it might be enough to remove the rings and lubricate them with petroleum jelly or find similar ones at a hardware store.
4. In models equipped with quick-disconnect taps, you need to disassemble the taps and check the sealing rings inside them.
5. In models equipped with priming pumps, you need to disassemble the external filter head and inspect the pump; leaks from under the pump sometimes occur.
6. A twisted sealing ring is a cause of leakage.
7. A carelessly washed external filter where sand gets onto the sealing ring is a cause of leakage.
8. Close the filter without taps or the tap block, allow the filter to close properly and let excess water escape.
External filter is noisy, what to do?
1. Check the filter installation; it is best to place the filter on a rubber mat. The filter should not touch the walls of the cabinet or any other objects that could amplify noise through resonance.
2. It is advisable to install the filter in a cabinet with doors, and ideally, provide additional soundproofing for the cabinet.
3. Check the filter intake pipe in the aquarium; air from an air stone very often gets into the filter, causing increased noise.
4. Check the impeller chamber; a dirty chamber or foreign objects can cause noise.
5. Check the impeller; the typical lifespan of an impeller is 2-3 years. Afterwards, the impeller begins to wear out, an ellipse forms, and this causes increased noise during operation. The lifespan of the impeller depends on operating conditions and timely maintenance. Do not run the filter without water, as this leads to dry running of the impeller and premature failure.
6. Noise can be caused by incorrect placement of filter media – experiment with media arrangement.
It often happens that you haven’t washed the pump for a long time, and then turned it off for a while during aquarium maintenance. When you turn it on again, it fails to start. It’s frustrating and confusing since it was just working. Most likely, dirt between the housing and the rotating impeller prevents the electric motor from starting. Since dirt accumulates on the impeller gradually, the following situation is possible: the pump is working, but due to a power outage for some reason it stops, and when power returns, the electric motor can no longer start it.
If you listen closely, you will make sure that the motor slightly vibrates and makes noise, but the impeller is not rotating. You need to carefully disassemble the pump and wash off the slime from the housing walls, shaft, and motor impeller. Then put everything back in place and turn on the filter.
The situation is much worse if a grain of sand gets into the gap between the impeller and the housing. The pump may make noise for some time and then stop, and the motor won’t even vibrate. If the motor wires are intact, you need to remove the grain of sand that has firmly jammed its impeller. This is not an easy task; you must act in a way that does not bend the pump shaft or damage the plastic parts.
If using a multimeter you find that current does not pass from one plug prong to the other, the pump should be replaced. Since all aquarium electrical equipment is sealed and manufactured with a high level of shock protection, you should never open and repair even a broken power cord. Electrical appliances designed to work under water must be in perfect working order.
Do not rush to buy a new filter when a problem arises. Very often, inexperienced aquarists at the very first breakdown cry that the filter is worthless and rush to buy a filter from another manufacturer. Nothing lasts forever; the average lifespan of a filter is 5 years, although many filters easily last 10 years or more. Filter quality does not depend on the manufacturer; frankly poor-quality manufacturers are not present on the market nowadays. Remember – an external filter for an aquarium is just a plastic bucket with a small motor, and very often the price of this plastic bucket is inadequately inflated. Just draw parallels with household appliances and think about whether it is worth overpaying for nothing, especially regarding brand-name manufacturers.
What if the electricity is turned off for a long time?
The impact of medications and fertilizers on biofilter performance. 
Last changes and additions were made on August 28, 2012.
