What an aquarium really costs

The price of the tank is only the start: an aquarium runs all year, day and night. The filter runs around the clock, the light has its photoperiod and, in a tropical tank, the heater keeps the water at 24-26 °C even in winter. On top of that come food, water conditioner, filter media, test kits and the water for changes.

This calculator adds every item into an annual and monthly cost and tells you how much of the electricity the heater uses. It works in any currency: enter the real prices from your bill and your purchases.

How the calculation works

• Heater: power × percentage of time it is on × 24 hours × 365 days. The thermostat switches it on only when needed, so the rated power is not enough: the on-time is what counts.
• Light: power × light hours per day × 365.
• Filter and pumps: power × 24 hours × 365, since they are always on.
• Water: tank litres × percentage changed per week × 52 weeks, at the price per cubic metre.
• Consumables: the monthly spend × 12.

The kilowatt-hours are multiplied by the energy price. The reading is based on the heater's share of electricity use, the most variable item.

The heater: the item that changes most

With a 120-litre tank, a 100 W heater, a 30 W light for 8 hours, a 15 W filter, energy at 0.30 per kWh, 25% of the water changed weekly at 2.5 per m³ and 10 a month of consumables:

The on-time depends on the gap between the water temperature and the room. In a heated home the heater may work little; in a cold room or near a window it can stay on for much of the day. To know it for sure, use a plug-in energy meter for a week.

Different tanks, different costs

Same prices, typical set-ups (the 300-litre tank with a 250 W heater, a 60 W light for 10 hours, 30 W of pumps, 20% weekly change and 20 a month of consumables):

Two things stand out. The water for changes costs very little: under 10 a year even for a 300-litre tank. The items that matter are the heater and the consumables, which in a small tank can exceed the electricity.

How much the light matters

Same 120-litre tank, 8 hours of light a day:

Switching from old fluorescent tubes to LEDs saves a few tens a year; fewer light hours also help against algae. The photoperiod should still suit your plants and animals.

The reading bands

• No heater: a cold-water or temperate tank; electricity depends only on lighting and pumps.
• Below 30%: the heater weighs little; lighting and pumps are the main lever.
• 30% to 50%: a significant item, but not dominant.
• 50% to 70%: the heater is the main item.
• 70% and above: the heater dominates electricity use.

How to cut the cost

• A lid reduces evaporation and heat loss.
• Keep the tank away from windows, doors and draughts.
• Do not set a higher temperature than the species you keep need.
• Choose LED lighting and a suitable photoperiod, on a timer.
• Buy consumables in larger packs if you really use them before they expire.

Limits of the calculator

The heater on-time is an estimate: it changes with the seasons, so use a yearly average. The calculator does not include buying the tank and equipment, livestock, plants, vet care or extra systems such as CO₂, chillers or skimmers: if you have them, add their power to the pumps or their cost to the consumables.

Frequently asked questions

How much does it cost to run an aquarium?

It depends mostly on the heater and consumables. A 120-litre tropical tank with a 100 W heater on 40% of the time, a 30 W light and a 15 W filter, with energy at 0.30 and 10 a month of consumables, costs about 295 a year.

How much electricity does an aquarium use?

In the 120-litre example about 570 kWh a year, more than half of it for the heater. Without a heater it drops to about 220 kWh.

Is the heater on all the time?

No: the thermostat switches it on only when the water drops below the set temperature. How often depends on the gap between water and room.

How do I measure the heater on-time?

With a plug-in energy meter: after a week, divide the heater's kWh by what it would use if it were always on.

How much does water for changes cost?

Very little: 25% a week on 120 litres is about 1.6 m³ a year, under 4 at the example price. Water conditioner belongs with consumables.

Is a cold-water tank cheaper?

Yes, because no heater is needed: in the example electricity drops from about 171 to about 66 a year.

Is it worth switching to LEDs?

Often yes: going from 60 to 20 W for 8 hours a day saves about 117 kWh a year, about 35 at 0.30 per kWh.

Does a bigger tank cost more?

Yes: in the example a 300-litre tank costs more than twice a 120-litre one, mainly for the heater, stronger lighting and consumables.

Does the calculator include buying the tank?

No, only running costs. Equipment and livestock should be counted separately.

Does it work in any currency?

Yes. Enter all prices in the same currency; kWh do not depend on the currency.