How to Fix an Aquarium Filter Pump (Not Working or Noisy)

If your aquarium filter pump has stopped, weakened or become noisy, the cause is almost always a clogged or stuck impeller, trapped air, or a blocked intake, and most of these are fixable in a few minutes without tools. A filter that hums but moves no water usually has an impeller problem; a filter that is loud usually has trapped air; a filter that is completely silent and dead may have a power or motor fault. This guide walks you through diagnosing the exact problem and fixing it step by step, plus how to handle leaks, when to replace the pump, and how to prevent failures in the first place.

A failing filter is stressful because your fish depend on it, but the good news is that the vast majority of pump problems are simple, common, and quick to solve. Work through the checks below in order.

First, diagnose the problem

Match your symptom to the likely cause before you start, it saves time.

Fix 1: Clean the impeller (the most common fix)

The impeller is the small magnetic rotor that pushes water, and it is behind the majority of pump failures. Sludge, grit or even a strand of plant matter wraps around it and stops it spinning freely.

1. Unplug the filter; never work on it while powered.
2. Open the pump housing and gently pull out the impeller.
3. Rinse off all debris and check that the small shaft (the pin it spins on) is not bent or broken.
4. Clean the impeller well with a soft brush, then refit it, making sure it seats fully.
5. Restart and check the flow.

This single fix resolves most “my filter stopped” problems. Make impeller cleaning part of your routine. See how to clean an aquarium filter.

Fix 2: Clear trapped air

Air pockets stop a pump moving water and cause loud rattling, especially right after a clean or water change. With the filter running, gently tilt or rock the unit to release trapped bubbles, or re-prime it by filling with tank water. In a canister, a few firm tilts usually burp out the air and the noise stops.

Fix 3: Unblock the intake

A clogged intake tube or pre-filter sponge starves the pump of water, causing weak flow. Remove and rinse the intake strainer and any pre-filter sponge in old tank water, and check the intake tube itself is clear of debris or snails.

Fix 4: Check the water level

If the water has dropped below the intake common with hang-on-back filters after evaporation, the pump sucks air instead of water and splutters. Simply top up the tank with dechlorinated water to restore the level above the intake.

Fix 5: Confirm the power

If the filter is completely silent, rule out the obvious: check the plug, socket, switch, and any extension board. A pump that hums but does not move water has an impeller problem (Fix 1); a pump that is totally silent and dead after power checks may have a failed motor.

Fixing a noisy filter

Noise is one of the most common complaints and almost never means the filter is broken. The usual culprits are trapped air (most common), a dirty impeller, or a water level that has dropped below the intake. Release the air, clean the impeller, and top up the water. The noise usually disappears. A noisy filter is never a reason to switch it off at night; see can you turn the filter off at night.

Fixing a leaking filter

Leaks are almost always a sealing problem, not a cracked body. The most common causes are a poorly-seated or dried-out lid o-ring on a canister or a loose hose connector. Reseat the lid, clean and lightly lubricate the o-ring with silicone grease (never petroleum jelly), and check all hose connections are tight. If the o-ring is cracked or perished, replace it.

When to replace the pump or filter

Replace the part or the filter if: the impeller is cracked or the shaft is broken (often a cheap replacement part); the motor is completely silent and dead after all power checks; or the filter body is cracked. For canisters, impellers, and o-rings are inexpensive wear parts, so a full replacement is rarely needed. If you do upgrade, browse the canister filter guide or the full Aquarium Filter collection.

Preventing filter pump failures

Most failures are preventable with light, regular maintenance: clean the impeller every one to two months, keep the intake and pre-filter sponge clear, maintain the water level above the intake, and rinse mechanical media before it clogs completely. A well-maintained pump runs quietly and reliably for years.

Frequently asked questions

Why is my filter pump not pumping water?

The most likely cause is a clogged or stuck impeller, followed by trapped air or a blocked intake. Clean the impeller and re-prime the filter.

Why is my filter so loud all of a sudden?

Usually trapped air or a dirty impeller. Release the air, clean the impeller, and make sure the water level is above the intake.

Can I run the filter while I fix it?

No, always unplug the filter before opening the pump housing or removing the impeller.

How do I clean the filter impeller?

Unplug the filter, remove the impeller, rinse off sludge and hair with a soft brush, check for damage, and refit it fully seated.

My filter hums but no water comes out what’s wrong?

Almost always the impeller is stuck or clogged, or there is an air lock. Clean the impeller and re-prime.

Why does my canister filter leak?

Usually a poorly-seated or dried-out lid o-ring, or a loose hose connector. Reseat and lubricate the o-ring and tighten the connections.

How do I fix weak filter flow?

Clean the intake, pre-filter sponge and impeller, and rinse clogged mechanical media. Weak flow is usually a blockage.

What lubricant can I use on filter o-rings?

Use silicone grease only. Never use petroleum jelly, which can degrade rubber seals.

My filter is completely dead — what should I check?

Check the plug, socket, switch and extension board first. If power is fine but it is silent, the motor may have failed.

How often should I clean the impeller?

Every one to two months, or sooner if flow weakens or the filter becomes noisy.

Why is my filter sucking in air?

The water level has likely dropped below the intake. Top up the tank with dechlorinated water.

Can a clogged filter damage the pump?

A severely clogged filter makes the pump work harder and run hot. Regular cleaning prevents strain and extends the pump’s life.

How long do filter pumps last?

A quality pump lasts many years with care. The impeller and o-rings are wear parts that may need occasional replacement.

Is it worth repairing a filter or buying new?

For canisters and quality filters, replacing a cheap impeller or o-ring is well worth it. Replace the whole unit only if the motor or body has failed.

Will the noise damage my fish?

Vibration and noise stress fish over time, so fix it, but never solve it by switching the filter off, which harms the bacteria.

Need a replacement part or a new filter? Explore options at the Filters & Filtration collection at Fish Bazaar.