Short answer
The micron rating is the smallest particle the robot's filter is rated to catch. Leaves and bugs are caught by anything; sand needs roughly 200 µm or finer; pollen and silt sit around 10–100 µm; the fine dust and early algae that cloud water are under 50 µm. Of the 24 robots here whose maker publishes a figure, the median is 150 µm — sand and grit, not dust. 28 publish none.
A micron is a thousandth of a millimetre; a human hair is somewhere around 70 microns across. Filter ratings describe the smallest particle the mesh or cartridge is designed to hold back, and the bands on this site follow what pool debris actually measures.
| Finest filter | What it catches | Robots here |
|---|---|---|
| 50 µm or finer | Fine dust, silt and early algae | 5 |
| 51–149 µm | Pollen and silt, not the finest dust | 1 |
| 150–250 µm | Sand, grit and leaves | 16 |
| Coarser than 250 µm | Leaves and bugs only | 2 |
A finer filter clogs faster. As it fills, suction drops, and a robot with a clogged ultra-fine layer cleans worse than one with a clean coarse basket. That is why the robots with 3 or 10 µm layers ship them as a second stage behind a coarse basket, and why their makers suggest running the coarse basket alone after a storm or in spring, when there is a lot of large debris.
The finest filter in the catalog is the Aiper Scuba S1 Pro at 3 µm. Several robots here offer an ultra-fine basket as an optional extra; this site counts only what is in the box, because that is what the price buys.
If the water is clear and the floor collects leaves, sand and bugs, a 150–180 µm basket does the job and stays unclogged longer. If the pool clouds after rain, collects pollen in spring, or has a fine-dust problem the sand filter lets back in, a sub-50 µm layer is worth having — and rinsing after every run.
Cordless floor+wall+waterline · 180 min, floor + walls
Cleans: Floor, walls, waterline
Cordless floor+wall+waterline · 180 min, floor only
Cleans: Floor, walls, waterline
Corded floor+wall · 120 min cycle
Cleans: Floor, walls
There is no single number, because what ends a robot's life is usually one part: a pump motor seal, a power supply, a battery, or a cable that has twisted beyond use. Brushes and drive belts wear out on a schedule and are cheap to replace. The warranty is the only lifespan figure a maker commits to, and here it runs from one year to three; 4 robots publish no term at all.
Some do: 38 of the 52 robots here list waterline cleaning. But a robot that "climbs walls" does not necessarily scrub the waterline — it may turn back a few inches below it. Look for a waterline mode or waterline scrubbing by name, and for a horizontal pass along the tile line rather than a vertical climb to it.
Every specification explained, with the numbers from the catalog behind each one.