The biofilm is the real target
Run a fingertip inside a reptile bowl that was only rinsed yesterday and you will feel it: a slick, almost soapy film that clings to the surface. That biofilm is a mat of bacteria, and topping the bowl up simply feeds it fresh water to grow in. Reptiles soak, drink and sometimes defecate in the same bowl, snakes drape through it, and lizards track substrate into it, so the film builds faster than in a cat's dish. Properly cleaning means physically breaking that film every day with a brush or scouring pad under hot water until the surface squeaks rather than slides. If the bowl still feels slick after scrubbing, it is not clean yet.
The daily method, bowl by bowl
Tip the old water away outside the enclosure — never into the substrate, where it seeds the damp corner with everything the bowl collected. Scrub inside, outside and under the rim, because bowls with a lip or a weighted base trap film in the overhang. Rinse with clean water, give it a shake, and refill with dechlorinated water: conditioner-treated or rested water protects the amphibians and the more sensitive reptiles, and does no harm to the hardy ones. Refill before the bowl goes back in, so you are not sloshing water across dry substrate and spiking humidity in a desert setup. A heavy, wide-based bowl resists tipping by a climbing snake, and a shallow profile suits small lizards that need to climb out as easily as they climb in.
The weekly deep clean and bowl condition
Once a week the bowl earns more than a scrub: wash it thoroughly, rinse it repeatedly until the water runs completely clean, and let it air-dry fully before refilling, because drying itself knocks back the bacteria a scrub loosens. Inspect the bowl while it is dry — hairline cracks in resin bowls, chips in ceramic glaze and roughened plastic all harbour film in places a brush cannot reach, and a bowl that never comes clean is a bowl to replace. Porous stone-effect bowls are the worst offenders; smooth glazed ceramic or stainless steel scrubs clean fastest. Keep two bowls per enclosure if you can, rotating them so one is always dry and ready, which turns the deep clean into a swap rather than a wait.
Placement and who does it
Position matters to how dirty the bowl gets: directly under a basking lamp it warms and grows film faster, and beside the feeding area it fills with substrate and food scraps, so a cool-side spot on a flat surface stays cleanest longest. For semi-aquatic species the bowl is also a bath, so size it for the animal to sit in fully. In a household where several people share reptile chores, the bowl standard is the thing that drifts — one person's rinse is another's scrub. Writing the daily scrub and the weekly deep clean as separate duties in KinsLe's Care Teams pins the standard down, so the bowl gets the full method even when the regular keeper is away.