# Fluval U2 Internal Aquarium Filter, Up to 110 Litres, 400 L/H Adjustable

Source: https://www.ranked10.co.uk/pet-supplies/best-aquarium-filter/fluval-u2
Ranked #1 in "Best Aquarium Filter 2026: Turnover Is the Only Number": https://www.ranked10.co.uk/pet-supplies/best-aquarium-filter

- Price: £36.00 (checked on Amazon UK on 2026-09-11)
- Amazon rating: 4.2 from 8,108 ratings
- Buy on Amazon: https://www.amazon.co.uk/dp/B001Q1HPGE?tag=ranked10-21

The Fluval U2 is the most-reviewed aquarium filter here: 8,108 ratings at 4.2 stars for £36.00, with adjustable flow up to 400 litres an hour, three stages of filtration and a stated tank size of 110 litres.

It takes first place because it is the only filter here with both numbers you need — the flow and the tank size — and three times the evidence of anything else. At 400 L/H for a 110-litre tank it runs at 3.6 turnovers an hour, the bottom of the recommended range.

## Specification

| Field | Value |
|---|---|
| Maximum flow | 400 litres per hour |
| Stated tank size | Up to 110 litres |
| Turnover at 110L | 3.6 times an hour |
| Filtration | Three stages with BioMax |
| Ratings | 4.2 from 8,108 |
| Price | £36.00 |

## Questions people ask

**What tank size is it for?**

Up to 110 litres, which at 400 L/H is 3.6 turnovers an hour: fine for a 60-litre tank at 6.7, marginal at the top of its range.

**What is the 4-6 times rule?**

The common advice that a filter should turn a tank's volume over four to six times an hour. No listing here states it, which is why you have to do the division.

**Is the flow adjustable?**

Yes, which matters in a planted tank or for fish that dislike current.

**Can I use it in a marine tank?**

The listing covers freshwater, marine and reptile use.

**Why is it first?**

Because it publishes both numbers, has three times the reviews of anything else here, and the brand means spares exist.

**How many ratings does it have?**

8108 at the time of collection, averaging 4.2 stars, with 66 per cent five-star and 11 per cent one-star.