Battery backup for an aquarium: air pump first, heater math second
Battery backup for an aquarium: Fluval publishes 2 to 4 watts for its air pumps and 100 to 300 watts for its heaters. That gap decides what you actually need.
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2,764.8 Wh with 3,840 W maximum output and a published 6,000+ cycles to 80 percent, the longest cell-life rating of the plug-in units on this page, which matters on a load you may cycle every winter. Against an air pump, a canister filter and a 200 W heater running half the time, that is a ceiling of about 23 hours.
4,096 Wh rated 4,000 W continuous with a published 8,000 W surge, expandable on one unit if the tank list grows. Against the same air pump, filter and half-duty 200 W heater that is a ceiling of about 34 hours, and about 216 hours if you drop the heater and run aeration and filtration only.
3,840 Wh with 6,000 W maximum output through its NEMA L14-30R port, sized for a whole essential-loads list rather than one aquarium. About 32 hours on a heated 65 gallon tank at half heater duty, and about 202 hours on aeration and filtration alone.
Every figure is a manufacturer datasheet spec. We have not lab-tested these units.
An aquarium looks like one backup problem and is really two, separated by roughly a factor of one hundred in watts. The device that keeps fish alive draws a few watts. The device that keeps them comfortable is rated in the hundreds, several times what a large refrigerator averages across a day. Size a battery for the first and you can buy almost nothing. Size it for the second and you are in whole-house territory. This guide works from Fluval's published wattages and from guidance published by Florida Sea Grant with a University of Florida fish health veterinarian. We have not tested any of these products, and the Amazon links above are affiliate links, disclosed at the top of this page.
What the components draw, from one maker's published tables
Fluval publishes wattage at 120V and 60 Hz for each product line, which makes it possible to line up three categories in the same units:
| Device | Rated for | Published wattage |
|---|---|---|
| A Series air pump | up to 50 US gal | 2 W |
| A Series air pump | up to 80 US gal | 3 W |
| A Series air pump | up to 160 US gal | 4 W |
| 107 canister filter | 10 to 30 US gal | 10 W |
| 207 canister filter | 20 to 45 US gal | 10 W |
| 307 canister filter | 40 to 70 US gal | 16 W |
| 407 canister filter | 50 to 100 US gal | 23 W |
| E100 heater | up to 30 US gal | 100 W |
| E200 heater | up to 65 US gal | 200 W |
| E300 heater | up to 100 US gal | 300 W |
The air pump rated for a 160 gallon tank draws 4 W. The heater rated for a 100 gallon tank draws 300 W. Those are the two ends of the same hobby, and no amount of battery shopping changes the ratio between them.
One honest gap in that table. The heater figures are nameplate ratings, not average draws. A heater is a thermostat with an element attached, and it runs only when the water is below setpoint, so its real average depends on how cold the room gets and how much water it has to hold. Fluval does not publish a duty cycle, and it could not sensibly do so, because the answer belongs to your house rather than to the product. Every heater figure below is therefore shown at several assumed duty cycles with the assumption stated, not at one invented number.
The triage, from a published source
Florida Sea Grant published a question and answer with Dr. Roy Yanong, veterinarian and UF/IFAS professor of fish health and aquaculture, on October 28, 2025, and it puts the priorities in an order that the wattage table above happens to reward.
Asked what to prioritise, the answer is temperature, oxygen and ammonia. Asked how to hold oxygen, the answer is aeration: "Good aeration happens when the surface of the water is moving, ideally with a turbulent or 'choppy' appearance. Still water means poor oxygen exchange." The recommended equipment is "a battery-powered air pump or a small generator," with a reminder to keep spare batteries even if you have a generator.
Two of the supporting points matter for sizing. Warmer water holds less oxygen, so heat and suffocation are the same problem rather than two. And ammonia rises when the biofilter stops, for which the published fix is mechanical rather than electrical: pull the biofilter media out of the filter and suspend it in an aerated container so the bacteria survive, then return it when power comes back. The guidance also suggests stopping feeding a day or two before an expected outage, on the basis that "fish can go about a week without food if they are in good condition," and keeping the tank dark to reduce stress.
The sign that the plan is failing is also published: gasping at the surface, which the article calls "piping," alongside abnormal behaviour and flashing.
Runtime arithmetic on a 65 gallon tank
Take Fluval's own published figures for a mid-sized freshwater setup: a 3 W air pump, a 307 canister filter at 16 W, and an E200 heater rated 200 W. Runtime at the ceiling is rated capacity divided by load. These use each unit's rated Wh rather than usable Wh and ignore inverter losses, the low-voltage cutoff and the station's own self-consumption, so real runtime is lower.
| Unit | Rated capacity | Pump and filter only, 19 W | Heater at 25 percent, 69 W | Heater at 50 percent, 119 W | Heater always on, 219 W |
|---|---|---|---|---|---|
| BLUETTI Apex 300 | 2,764.8 Wh | 145.5 h | 40.1 h | 23.2 h | 12.6 h |
| Anker SOLIX F3800 Plus | 3,840 Wh | 202.1 h | 55.7 h | 32.3 h | 17.5 h |
| EcoFlow DELTA Pro 3 | 4,096 Wh | 215.6 h | 59.4 h | 34.4 h | 18.7 h |
| Jackery Explorer 5000 Plus | 5,040 Wh | 265.3 h | 73.0 h | 42.4 h | 23.0 h |
| EcoFlow DELTA Pro Ultra | 6,144 Wh | 323.4 h | 89.0 h | 51.6 h | 28.1 h |
The first column and the last column are different products in every practical sense. Aeration and filtration together are a load any of these units carries for the better part of a week. The same tank with its heater on a cold night is a load the smallest unit here carries for half a day.
The column you should actually plan against depends on the season and the room, and neither is a spec. If the outage is in July in a warm house, the heater may barely fire and the first column is close to the truth. If it is January in an unheated room, the last column is closer, and the answer is probably to insulate the tank rather than to buy a fifth kilowatt hour. Our winter outage guide covers the general version of that trade.
Where a battery air pump beats a power station
For a great many tanks the correct purchase is not on this page. A 2 to 4 W air pump is a load that a handful of alkaline cells carries for days, which is why the published extension guidance names a battery-powered air pump first and a generator second, and never mentions sizing a bank of storage. If the tank is unheated, or heated but in a room that stays in the range the same guidance calls comfortable, aeration is the whole job and the whole job costs almost nothing.
The units above earn their place in three situations. A reef tank, where the published advice is that more oxygen and lighting are needed and a generator is preferable. A heated tank in a cold-climate winter outage, where the 100 to 300 W heater is the load and the arithmetic above is the arithmetic. And a household where the aquarium is one line on a list that already includes a refrigerator and a freezer, in which case the tank is a small addition to a decision made elsewhere and the plug-in backup comparison is the right page.
One specification worth checking if you go the power station route: switchover time. A canister filter that stops and restarts is a minor event, but a unit with a published sub-10 ms UPS switchover keeps the surface moving without a gap. Which makers publish that figure, and which only mention it in page copy, is covered in our transfer times guide.
What to settle before you buy
Write down three numbers off your own equipment: the heater's nameplate wattage, the filter's wattage, and the air pump's wattage. Fluval prints all three on its product pages and most competitors print at least the heater. Then decide, honestly, whether the heater belongs on the list at all given your climate and the season your outages arrive in. That single decision moves the answer by roughly a factor of ten, which is larger than the difference between any two products on this page.
Every figure above is a published claim recorded with its source: device wattages from Fluval's US product specification tables for the A Series air pumps, 07 Series canister filters and E Series heaters, and the husbandry guidance from Florida Sea Grant's published question and answer with Dr. Roy Yanong of UF/IFAS, all read August 19, 2026. Power station capacities come from each maker's own spec table. The runtime numbers are arithmetic on those claims under the duty-cycle assumptions stated, not measurements we made, and not a promise about your tank or your fish.