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  • Writer's pictureStewart Kessel

Freshwater Aquarium Running Costs

Updated: Jan 8

How Much Does It Cost to Run your Freshwater Aquarium?

Often those thinking about setting up a fish tank will be concerned about the cost of running the aquarium once it has been set up. This has become even more of a focus with the ever-increasing energy costs.

Many fish keepers are anxious that running the lighting, filters and heaters in their cherished freshwater tropical aquarium will become too expensive with the higher cost of electricity.

Aquarium electrical running cost

Like any hobby or keeping of animals, there is a necessary cost associated. But this must be balanced against the pleasure and well-being gained from that activity. Clinical trials show that keeping fish and having an aquarium in your home positively affect health and mental well-being. Studies show that observing and maintaining an aquarium can help reduce blood pressure, anxiety, and stress. Fishkeeping and the upkeep of an aquarium can also be a rewarding and educational hobby for persons of all ages. Most people will say these benefits outweigh the costs, but how much does running a typical freshwater tropical aquarium cost?

Before calculating the cost of running your tropical freshwater aquarium, let's broadly identify the two main cost areas. Firstly, the energy costs to run all the equipment, and secondly, the maintenance and general upkeep of the aquarium.

Aquarium Energy Costs

This is the main area of concern for many newcomers to the hobby and has become even more of a focus due to the increasing cost of electricity.

The primary electrical equipment that you will need to consider when calculating the cost of running your aquarium will be the following:

  • Filter (internal or external)

  • Lighting

  • Thermostatic Heater

Depending on the specifics of your freshwater aquarium set-up, you may be running other ancillary equipment that also needs consideration, including, for example:

  • Air pumps

  • Automatic feeders

  • CO2 solenoid (e.g. automated CO2 injection)

  • Automated dosing pumps (e.g. for plant fertilisers)

  • Remote monitoring devices (e.g. cameras, online water tests)

Calculation of aquarium energy consumption and cost

As with other household electrical goods, the cost of running the above aquarium equipment is determined by the amount of electrical power they consume, measured in Watts and the time that they are running and hence drawing on that power. This is typically expressed in kilowatt-hours (kW hrs).

The equipment manufacturers will quote energy consumption as part of their products specification. Reviewing the supplied operating instructions or their website will usually lead you to this information.

You can then obtain an estimated running cost by looking at the quoted wattage for each piece of equipment and the length of time they operate.

If you look at your last energy suppliers bill, it will quote the price per unit of electrical energy. That is, it will express the cost as £ per kW hr.

It is then a simple task for each piece of electrical equipment to multiply the cost of a kilowatt-hour by the number of kilowatt-hours it uses for a given period.

For example, let us consider the equipment used on a typical 240-litre (approx. 4-foot) freshwater aquarium.

Example 1: Cost of running an External Aquarium Filter

An aquarium filter, whether internal or external, will need to run continuously. It is, therefore, wise to look at the device's energy efficiency when making the initial purchase. However, it is critically important that the filter is correctly rated for the aquarium's water volume to ensure sufficient turnover of water and efficient filtration.

For this example, we will consider a typical external filter rated at 20 Watts, e.g. Fluval 407 external filter (240 Volt/50Hz).

Power rating: 20 Watts

Operating period: 24 hours daily (filter should be run continuously)

Electricity charge: £0.34 per kW hr (1st Oct 2022 UK capped price)

Calculation: 20 W = 0.02 kW (1 kW = 1,000 W)

0.02 kW x 24 hours (per day) = 0.48 kW hr

Daily cost = 0.48 kW hr x £0.34 per kW hr = £0.1632

Example 2: Cost of running an Aquarium LED Lighting Unit

With the aquarium lighting, the total wattage of the light unit will be quoted, which can then be converted into kilowatts. You will then need to determine the photoperiod, i.e., the time the lights are on during the day. Typically for most aquariums, the lighting period will be approximately 8 hours a day.

For this example, we will consider an LED lighting unit rated at 27 Watts, e.g., Fluval Aquasky 14533.

Power rating: 27 Watts

Operating period: 8 hours daily (typical photoperiod)

Electricity charge: £0.34 per kW hr (1st Oct 2022 UK capped price)

Calculation: 27 W = 0.028 kW (1 kW = 1,000 W)

0.027 kW x 8 hours (per day) = 0.216 kW hr

Daily cost = 0.216 kW hr x £0.34 per kW hr = £0.0734

An additional consideration with some LED lighting units is that their power can be reduced. This would also need to be factored into your calculations.

Example 3: Cost of running an Aquarium Thermostatic Heater

The selection of an aquarium thermostatically controlled heater is based on aquarium water volume. The correct wattage of the heater is required to ensure adequate and stable heating of the aquarium water. A good rule of thumb is that an aquarium heater's wattage needs to be 1 W for every litre of water.

Calculating the cost of running the heater is more problematic as it is difficult to determine how often and long the thermostat switches on the heater. In a heated room in a house, the aquarium water may retain its heat much longer than, for example, in an unheated or poorly insulated room. So, the time the heater is on will be different for the same aquarium in different environments. As an approximate guide in a typically centrally heated house, the heater will likely be on 4 hours in total a day. This figure can often be more in winter if you do not run your house heating overnight.

Power rating: 250 Watts

Operating period: Approx. 4 hours daily (see above)

Electricity charge: £0. 34 per kW hr (1st Oct 2022 UK capped price)

Calculation: 250 W = 0.25 kW (1 kW = 1,000 W)

0.25 kW x 4 hours (per day) = 1.0 kW hr

Daily cost = 1.0 kW hr x £0.34 per kW hr = £0.3400

Therefore, considering just the above primary electrical equipment, the running cost of a typical 240-litre freshwater aquarium would be:

Daily cost

Annual cost







Thermostatic Heater



£0.5766 per day

£210.459 pa.

Following the above process for your specific equipment and any additional electrical items will give you a reasonable approximation of the energy costs when running your freshwater aquarium.

"Use a Power Usage Meter to determine a more accurate electrical energy usage"

If you are seeking more accurate electrical energy usage for your aquarium, it is possible to use a power usage meter. These simple devices plug into your electric mains socket, and then the equipment you wish to monitor plugs into them. As with any electrical item, carefully follow the manufacturer’s instructions and ensure you do not overload the device by, for example, connecting multiple items to the same monitoring device.

Maintenance & General Upkeep of the Aquarium

In addition to the energy cost, there are other expenditures in the maintenance and upkeep of your tropical freshwater aquarium. Assuming you have all the necessary maintenance equipment, the following are the primary consumable items that you need to consider:

Fish foods

Remember to select foods that meet the dietary requirements of your livestock. A variety of foods is also good, including some live foods. Remember, the cheapest is not always the best choice and could cost you more in the longer term.

If buying bulk to help reduce costs, remember to store it under suitable conditions. Dried foods will often absorb water from the atmosphere if left in unsealed containers, significantly reducing their lifespan.

Water conditioners/treatments

A water conditioner to de-chlorinate tap water during regular water changes is required. Although all the leading brands similarly neutralise chlorine and chloramine, some of the seemingly lower-cost options will only act on the former. If your local water authority uses chloramines in your water supply, you must therefore be sure to purchase the appropriate water conditioner.

Test Kits

When establishing a new aquarium, a good water test kit is essential when cycling a new aquarium filter. But testing your aquarium water regularly in an established set-up will also help ensure that your fish and other livestock remain healthy. Changes and fluctuations in the aquarium water chemistry can stress your fish and make them more susceptible to disease.

A good kit with tests to measure ammonia, nitrite, nitrate, pH and water hardness (KH and GH) is preferable.

CO2, plant fertilisers

If you have live plants in your aquarium, using an aquarium plant fertiliser is sensible to keep them in good growth. If you maintain a well-planted aquarium or aquascape, then CO2 injection may also be preferable, so you need to factor into your running cost replacement of the CO2 cylinder.


Totalling the cost of the above consumables, in addition to your calculated energy costs, will give you a good understanding of the running costs of your freshwater aquarium. Inevitably there may be other costs, such as additional livestock or changes to the aquarium décor and hardscape, but these are not essential costs.

Without a doubt, the increasing energy costs have pushed up the cost of running an aquarium, but many will still say that the benefits of ownership out-way those costs. Not only can you enjoy a slice of nature in your home and the educational value it can bring, but studies show that observing and maintaining an aquarium can help reduce blood pressure, anxiety, and stress.

If you are still not convinced, consider comparing the cost of your chosen pastime to the cost of the hobbies of others, such as playing golf or gardening.

Happy fishkeeping.

Author: Stewart Kessel CChem, MRSC

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