How do I calculate the right filter and pump size for my fish tank?

When selecting the best filter and pump for your aquarium fish tank, you must consider:
Which type of filtration system is most suited for the aquarium you want, what is the desired flow-rate for your aquarium livestock, what additional equipment will be set up, and what sort of plumbing will be installed.

Starting with filtration, you will need to know:
1. The Volume of Your Aquarium
You can easily calculate your aquarium’s water volume by using the tank’s dimensions. Simply multiply the tank’s length x width x height / 1000. The result will equal how many litres of water your fish tank holds.
Example: You have a fish tank that measure 150 centimetres in length, 55 centimetres in width, and 55 centimetres tall.
150cm x 55cm x 55cm / 1000 = 453.75
Your aquarium capacity is 453.75 litres.
For the cleanest, healthiest tropical aquarium set-up, we recommend that all the water in the aquarium flows through the filter 4 times per hour.  
453.75 x 4 =   1815
This means that the preferred filter for your fish tank has a flow rate of at least 1815 litres per hour.
There are a few different types of filters on the market and the type of filter you choose is going to dictate which aquarium water pump you are going to need. Consider the following set-ups:
  • Hospital or breeding tanks – Sponge/air-powered filters are most effective. Since these filters have no moving parts in the tank, small fish and newly hatched fry cannot be drawn into the filter, resulting in lower mortality rates. They also provide minimal disturbance to the water, reducing agitation for sick fish.
  • Small tanks (under 30 gallons), with a small number of fish – Internal filters or power filters are most effective. These filters are powerful enough to maintain quality water conditions, yet gentle enough to keep small fish safe. For small tanks, our 700IF+ Internal Filter is ideal, with a fully submersible filtration pump, directional water flow outlet, venture pipe aeration and UV to help control bacterial issues and green water.
  • Large tanks (over 30 gallons), with a large number of fish – Larger tanks need more power to maintain healthy fish, as the fish place a higher strain on the filter. External canister filters or wet/dry filters are perfect for this. These boast efficient operation, easy access, and more customisation options. For large tanks, our 2000 EF+ External Filter is ideal, with three filter media trays, one customisable tray, easy priming, a spray bar for flow distribution and UV to help control bacterial issues and green water.
When choosing an aquarium water pump for your set-up, you will need to have an idea about what flow rate you need:
Now that you know which type of filter you will need, you will need to think about the desired flow rate in your aquarium will be. Some aquarium livestock require a strong flow rate, like marine fish, and some aquariums, like planted tanks, require much less flow. You will need to research the flow rate in which your fish / aquarium plants will prefer. You will need to adjust your pump size accordingly.
Consider the type of plumbing you have in your aquarium. Some set-ups are quite simple while others have more complex designs using aquarium sumps or external equipment. Whether your aquarium filter system is directly underneath your tank or across the space of a room, you will need to take into consideration the distance the pump will be required to move your aquarium water. The greater the distance, the stringer the flow rate your pump will have to have.
Many fish tanks have additional equipment that requires the tank water to run through them. Extra filtration, UV sterilisers, protein skimmers, etc., will need water flow; meaning aquarium pump flow rate will need to be greater than what is needed for the main aquarium inhabitants.
We cannot stress enough how important research is when shopping for aquarium filters and pumps. If you want to set up an extremely specialised fish tank, requirements will be different. If you need any further information and advice please contact our sales team on 01895 813 000.