Aquarium Pump Buying Guide: How to Choose the Right Fish Tank Pump

Every aquarium relies on a pump to keep water moving, oxygenated and clean. Whether you're setting up a new tank or replacing a tired unit, understanding how aquarium pumps work will save you money and protect your fish. Most home aquariums use one of two setups: an internal filter that sits inside the tank, or an external filter pump (also called a canister filter) that sits below or beside the tank and draws water through hoses. Both types combine a water pump with mechanical, biological and sometimes chemical filter media to keep water clear and safe.

The key decision when buying an aquarium pump is flow rate, measured in litres per hour (L/H). As a rule of thumb, aim for the pump to turn over your entire tank volume at least 4 times per hour, so a 100-litre tank needs a pump rated around 400L/H or more, though heavily stocked or fast-flow-loving fish may need higher. Below we answer the most common questions people ask when choosing a filter pump, tank filter, or fish tank pump and filter combination, so you can pick the right one first time.

What is the difference between an aquarium pump and an aquarium filter?

A pump simply moves water, while a filter pump combines a water pump with filter media (sponges, ceramic rings, floss) to clean the water as it circulates. Most aquarium products sold as filters, such as an internal filter, include a built-in pump so you don't need to buy them separately.

What size aquarium pump do I need for my fish tank?

A good starting point is to choose a pump that can turn over your total tank volume around 4 times per hour. For example, a 200-litre aquarium would suit a pump rated at roughly 800L/H, such as the 1000 L/H Submersible Aquarium Water Pump with Flow Controller, which lets you fine-tune the flow down if needed.

Should I choose an internal or external filter pump?

Internal filters, like the AllPondSolutions 1000L/H Aquarium Internal Filter, are compact, affordable and easy to maintain, making them ideal for smaller or medium tanks. External filters, such as the AllPondSolutions 1000L/H + 9W UV Aquarium External Filter, sit outside the tank, offer larger filter media capacity and are better suited to bigger aquariums or heavier stocking your tank.

Why is my aquarium pump not producing enough flow?

Reduced flow is usually caused by a clogged impeller, dirty filter media, or a blocked intake strainer. Regularly cleaning the impeller housing and rinsing filter sponges in tank water (never tap water, which can kill beneficial bacteria) will restore normal flow.

Can I add UV sterilisation to my aquarium filter pump?

Yes, many external filters include an integrated UV clarifier, and UV bulbs such as the AllPondSolutions 9w PLS UV Bulb can also be fitted to compatible units to help control green water and free-floating algae and parasites in the tank.

How often should I clean or replace my aquarium pump and filter media?

Rinse mechanical filter media (sponges/floss) every 2-4 weeks in old tank water, and check the pump impeller for debris at the same time. Biological media such as ceramic rings should be left largely undisturbed and only rinsed gently, as it houses the beneficial bacteria that keep your tank cycled.