Water and friction do the whole job
The green film on frog-tank glass is algae and biofilm growing where light, water and nutrients meet — it is cosmetic, mostly harmless, and removable with nothing but water and rubbing. Chemical cleaners are banned from the inside for a simple reason: a frog's skin is a drinking surface, permeable to whatever dissolves in its water, so even a rinsed residue can end up inside the frog. The good news is that wet glass gives up its film easily. Algae that feels immovable on a dry pane wipes away under a wet pad, and mineral crust softens after a few minutes under a soaked cloth. Chemistry was never the active ingredient — moisture and patience were.
Tools that stay inside the rules
Keep a small kit that lives beside the tank and touches nothing else: a soft sponge or an algae pad rated for your tank material — gentler pads for acrylic, which scratches if you so much as look at it with a scourer — a blade scraper designed for aquarium glass for the crusty waterline band, and a plain microfibre cloth for the outside. Rinse the pad in dechlorinated water before it goes in, because it has been drying in room air and collecting dust and whatever your hands carried. Between uses, let the kit dry fully; a pad stored wet in a closed box grows the very film you are fighting.
Cleaning around a frog still in residence
You rarely need to move the frog for glass work, and a frog left alone is a calmer frog. Time the job to a partial water change: siphon the level down a hand's width, which exposes the worst of the waterline crust, then wipe the inside panes in slow, long strokes from the waterline upward, rinsing the pad in the bucket of removed tank water as it loads up. Slow matters — fast wiping just redistributes the film as a green haze in the water column. Leave the back pane if your frog likes its algae grazing, and keep hands that have touched soap or lotion out of the tank entirely. Work while your frog is settled in its usual hiding spot rather than mid-hop around the tank, and pause if it starts climbing away from the pad repeatedly — the remaining film will keep until the next change, but a panicked frog leaping at an open lid is a genuine problem.
Slowing the film between cleans
You cannot stop algae, but you can starve it. Most frog-tank film is light-driven: shorten the lit hours slightly, move the tank out of direct sunbeams, and wipe new film weekly while it is thin rather than monthly when it has crusted. Overfeeding feeds the water, and the water feeds the glass, so uneaten food removed the same evening pays off on the pane a week later. The outside of the glass can take a cloth dampened with plain water for fingerprints. Build the wipe into the same visit as the water change, and in KinsLe the Care Teams list pairs glass duty with change day, so the panes get their two minutes every single week.