Set up for a calm cleaning session
Wash and rinse your hands and forearms thoroughly, with no soap residue, lotion, or spray anywhere that will enter the water, and lay out a plain aquarium-safe algae pad or scraper plus a towel for drips. Angelfish read sudden movement above the tank as a possible predator, so open the lid slowly, let the fish register your hand, and give a breeding pair a wide berth before you touch the glass at all. Switch off bright room reflections if you can; a clear view through the pane tells you which patches are film algae and which stubborn spots need a second pass.
Work the panes in slow, overlapping strokes
Press the pad flat and draw it down from the waterline in long, unhurried strokes, rinsing it in a bucket of removed tank water whenever it loads up with green film. Top-down strokes let loosened algae drift to the substrate where your next siphon can lift it, instead of clouding the whole water column at once. Keep your free hand still and your movements telegraphed, because an angelfish that panics can dash sideways into driftwood and damage a fin or scale; if the fish bunch tightly and darken, stop, rest your hand motionless, and resume once they relax.
Treat breeding territory as a no-go patch
Angelfish pairs lay eggs on vertical surfaces, including the glass itself and broad leaves pressed against it, and devoted parents will fan and defend that patch for days. Scraping through a clutch or crowding a guarding pair stresses the parents and usually ends the spawn, so simply leave that section of algae standing until the eggs hatch or are removed by the parents themselves. A slightly green corner for a week is a small price for an undisturbed pair, and the missed patch can be caught up in one pass once the territory is empty again.
Mind the scraper around tall fins and acrylic
On glass tanks a firmer blade-style scraper handles crusty spots, but on acrylic only a soft pad is safe, since a single trapped grain dragged under a hard edge scores a permanent line. Keep magnetic cleaners moving slowly and never park one where an angelfish rests against the glass, as a curious fish can be pinched when the halves snap together. Work around silicone seams with lighter pressure, and check the pad for trapped gravel after cleaning low near the substrate, because one dragged stone scratches more glass in a second than algae ever will.
Algae that returns in days is a lighting message
A gentle green film over a week or two is ordinary; panes that fuzz up again within days are reporting too much light, uneaten food, or both, and scraping harder will never fix that arithmetic. Shorten the lighting period a little, feed so nothing reaches the substrate uneaten, and let the cleaning interval stretch back out. When an angelfish's regular glass-cleaning day is logged in KinsLe's Care Teams as an assigned duty marked complete with a timestamp, everyone in the household can see at a glance whether this week's pane was actually done or only intended.