Best Aquarium Filter 2026: Turnover Is the Only Number

The most-reviewed filter in this ranking by a factor of three: 8,108 ratings at 4.2 stars with 66 per cent five-star and 11 per cent one-star, for £36.00. It is an internal filter with an adjustable flow of up to 400 litres an hour, three stages of filtration using Fluval's BioMax media, and a listing that also covers marine and reptile use.

Its headline claim is a tank size: up to 110 litres. That is the useful number in this category, because a flow rate alone decides nothing. The standard advice is that a filter should turn a tank's water over four to six times an hour, and 400 L/H against a 110-litre tank is 3.6 times — the bottom of that range. Against a 60-litre tank it is 6.7 times, which is comfortable. One filter, bought for two different tanks, doing two different jobs, and this listing gives you both numbers to work it out.

The reviews are about reliability and control: brilliant filter, would buy again, the flow is powerful. The 11 per cent of one-star ratings is the highest rate among the well-reviewed filters here, mostly about impellers and noise after a year of use. At £36.00 it is the dearest filter in this ranking and the one with the most evidence behind it.

The first product in Amazon's aquarium filter category, with 634 ratings at 4.3 stars, 67 per cent five-star and 7 per cent one-star, for £19.99. It is a fully submersible internal filter rated at 700 litres an hour for tanks of 60 to 150 litres, with a spray bar for surface agitation, filter media included and — unusually — a spare impeller in the box.

Run the division and the two published numbers work together. At 700 L/H a 100-litre tank is turned over seven times an hour and a 150-litre tank 4.7 times: both inside the four-to-six-times range that aquarium keepers use, which is rare here. Compare the 1,200 L/H filter below, whose stated range of 100 to 400 litres spans twelve times to three times turnover, and the value of a published range becomes obvious.

The spare impeller is the detail that shows the maker knows its own product: the impeller is the part that wears and the usual reason a filter stops, and shipping one with the filter is worth more than a longer warranty on paper. The reviews are short and satisfied — brilliant suction, very quiet, water crystal clear constantly — and a one-year limited warranty is stated, which several filters here do not bother with.

The most familiar filter in British fishkeeping, and the one that shows the hole in this category's data: 4.2 stars from 2,752 ratings, £15.69, with a stated maximum tank size of 68 litres, four stages of filtration, directional and flow-rate controls — and a 7-watt pump whose litres per hour the listing never gives.

That omission is the point. The Fluval above publishes a flow of 400 L/H and a tank size of 110 litres, so you can work out the turnover; the NICREW publishes 700 L/H for 60 to 150 litres. This listing gives you a tank size and a wattage instead, and wattage is not flow: a 7W pump might move 200 litres an hour or 500 depending on its design. Without the number, a buyer cannot tell whether this filter turns a 68-litre tank over three times an hour or eight.

What 2,752 ratings do tell you is that it works in the tanks it was designed for. The reviews describe it as powerful for its size, easy to fit, reasonably quiet and worth the money — a reputation that has kept the model on sale for years. Buy it for a standard community tank of 60 litres or less; if you stock heavily or keep messy fish, buy one of the filters that publishes its flow.

The best value among the small filters: £13.99 with 4.3 stars from 2,267 ratings, a flow of 150 litres an hour for tanks around 20 litres, and a box containing the pump, a carbon cartridge, filter foam, an air tube, an impeller and a spare impeller — the whole maintenance kit for a small tank.

The arithmetic works at both ends. A 20-litre tank at 150 L/H is 7.5 turnovers an hour, which is generous; a 40-litre tank is 3.75, under the four-to-six range — and one reviewer here runs it on a 40-litre tank and calls it quite powerful for its size, which shows that a lightly stocked tank tolerates the bottom of the range.

Its party trick is the spray bar: the listing says the filter can also work as a wave maker, a fountain pump and an oxygen supply, which is a lot of jobs for a 290g unit measuring 16cm across. For a nano tank, a quarantine tank or a shrimp setup this is the filter to start with, and the spare impeller means it will not stop on a Sunday evening.

The filter in this ranking whose two published numbers agree with the rule: 200 litres an hour for tanks of 20 to 40 litres, which is ten turnovers an hour at the bottom of that range and five at the top. That meets the four-to-six-times guidance no listing here states — at the upper end of its tank size — and it carries 4.3 stars from 2,940 ratings with 64 per cent five-star and 5 per cent one-star, for £15.99.

It shares its category badge with the Magi700 above: both listings show first place in Amazon's aquarium filter category, which is what happens when one brand's two models swap places between page loads. They are the same design at different sizes, both ship a spare impeller and both include media and a spray bar, and the 200 costs £4 less than the 700.

What decides between them is the tank. Up to 40 litres, this is the one: at 200 L/H it turns a 30-litre tank over 6.7 times an hour and a 40-litre tank five times. Put the 700 on the same 40-litre tank and you are at 17.5 turnovers, which is a whirlpool for small fish. The listings give you the numbers; the rule is the part you bring.

The largest flow in this ranking at 1,200 litres an hour, with a 10-watt UV steriliser and a timer, sold for tanks of 100 to 400 litres at £32.99. It carries a perfect five stars from 19 ratings, the smallest sample here by a distance: nineteen people have never watched a filter run for a year.

Its claimed range is the number worth examining. At 1,200 L/H a 100-litre tank is turned over twelve times an hour — twice the top of the recommended four-to-six range — and a 400-litre tank three times, below the bottom. So one filter is offered as suitable for two tanks four times apart in size, and the honest answer is that it suits neither end: it is a filter for a 200 to 300-litre tank, where the same pump delivers four to six turnovers.

The UV lamp is a genuine feature for green water, and a 10-watt tube with a visible window and a timer is more than most rivals offer. Buy it for a large tank if the flow suits the volume, and treat both the perfect rating and the range with the caution 19 reviews deserve.

A double sponge filter for £25.99 with 3.9 stars from 735 ratings and 13 per cent one-star, the highest complaint rate in this ranking. Its size specification is a wattage: 3W for 35 to 150 litres. Three watts does not tell you the flow, and a pump that size cannot turn a 150-litre tank over four times an hour, so the upper half of that range is optimistic.

What sponge filters do is biological filtration, and that is worth understanding before buying one. The ribbed foam holds the bacteria that process fish waste, and the maintenance rule is to rinse the sponge in tank water rather than under a tap, because chlorine kills the colony you are cultivating. The listing describes both physical and biological filtration, which is accurate, and the motor is an upgrade on the air-pump versions that need an external bubbler.

The positive reviews are from long-term owners: had it almost a year and still going strong, the extra set of sponges will come in handy, it wobbles a bit and could use more suction. For a shrimp tank or a fry tank, where gentle flow matters more than turnover, a sponge filter is the right tool. For a community tank, buy one with a published flow rate.

The cheapest filter here at £10.97, and the one that makes the range problem plainest: 200 litres an hour, for tanks of 3 to 40 litres. At 3 litres that is 66 turnovers an hour, which is a jacuzzi; at 40 litres it is five, which is right. The listing is honest about the wattage — 3W — and about its two outlets, a spray pipe and a standard one, but one filter cannot be ideal across a thirteen-fold range.

It ranks fifth in Amazon's aquarium filter category on only 35 ratings, which is the same contrast we found in the bird feeder ranking: ranks move on recent sales, and a cheap product can hold a high rank with very few reviews. Ten per cent of those 35 disagree with the rest, mostly about noise.

The reviewers who are happy describe exactly the use it suits: a small tank, a shrimp setup, a quarantine box. One suggests lowering it slightly to quieten it, which is the sort of tip that comes from a filter small enough to sit anywhere. At £10.97 it is the cheapest way here to filter a tank of under 20 litres properly.

A filter that contradicts itself in its own listing: the title promises 6-layer filtration, and the first bullet describes a 4-layer sponge system with coarse, medium and fine sponges. It costs £32.54, weighs 790g and carries 4.3 stars from 27 ratings with 12 per cent one-star — a small sample with a high complaint rate.

Counting layers is how this corner of the category competes. The listing below claims 4-in-1 and 5-in-1 in different places; this one promises six layers and shows four. Layer count is a marketing number rather than a measured one, because what matters in filtration is the volume of media and its surface area for bacteria, and neither figure is published anywhere here.

The UV lamp is the feature that justifies the price, and the reviews are positive about it: a very good filter for the price, no noise, and the UV option is very good value. With 27 ratings, though, it sits at the bottom of a ranking where the leading filter has 8,108. Buy it for the UV and the price rather than the layer count.