Bring a sturdier pad than a tropical tank needs
Goldfish tanks grow algae with enthusiasm: generous feeding, abundant waste, and bright viewing lights produce not just soft green film but hard green spot algae that shrugs at a gentle wipe. Use a firm aquarium-safe pad, and on a glass tank a blade scraper is a legitimate tool for the crusty patches, held at a shallow angle and pushed in short, controlled strokes. On acrylic, stay with pads made for acrylic and accept slower progress, because a blade or a gritty pad will haze the surface permanently. Rinse hands well beforehand, and skip any sponge that has ever met a cleaning product.
Work around a very interested audience
A goldfish does not hide from cleaning; it assembles. Expect the whole group to follow the pad, mouth at your fingers, and investigate every loosened ribbon of algae as a possible snack, which is harmless but slows the work if you keep stopping. Settle into a steady rhythm, front pane first, then the viewing sides, rinsing the pad in a bucket whenever it clogs. Dislodged algae drifting in the water is fine for the fish to pick at briefly, but the bulk of it should leave with the water change that follows, not settle into the gravel of a fish that produces this much waste already.
Scrub first, then change the water
Sequence matters more in a goldfish tank than in most: cleaning stirs waste and algae into the water column, so scrub immediately before a partial water change and let the siphon harvest everything you loosened, including the mulm that collects along the front gravel line. Run the pad down to the substrate edge but not into it, because goldfish gravel traps grit that scratches glass when dragged upward. While you work, glance at the fish themselves; a cleaning session is a rare close look at flanks, fins, and eyes, and goldfish are cooperative models who will present every side to you.
Fast-returning algae points at the feeding hand
If panes film over again within days, the scraper is not the problem. Goldfish are chronically overfed because they beg convincingly, and every surplus pellet becomes algae fertiliser; tightening portions so meals disappear within a couple of minutes slows regrowth more honestly than any scrubbing schedule. Light duration is the second lever, and trimming it gradually beats blacking out the tank, which only shocks the routine. Persistent slime on the fish themselves, gasping at the surface, or algae exploding alongside cloudy water calls for water testing first and aquatic veterinary advice if the fish look unwell.
Keep one scrubbing schedule for a high-upkeep tank
Because a goldfish tank visibly needs cleaning more often than a lightly stocked one, different helpers tend to scrub on impulse, and the tank ends up disturbed three days running and then ignored for a fortnight. A single named cadence, with the water change attached, evens that out. In KinsLe, Care Teams lets you assign the goldfish scrub-and-change as one recurring duty and timestamp its completion, so whoever is on tank watch can see the panes were done yesterday and leave the fish in peace today.