Reassess what a pleco actually eats
The idea that a pleco is a living algae scraper survives because plecos do rasp at surfaces all day. What they remove well is soft film — the slippery green-brown coating on glass, wood and rock. What they barely touch is the hard green spot algae that dots mature glass, and many common plecos grow more interested in protein and prepared food as they age, grazing less just as they get bigger. Add that a single fish can only work so many hours, and a tank with strong light and rich water grows algae far faster than one mouth can harvest it. Expecting the pleco to keep up alone was never a fair job description.
Take over the glass with a regular scrape
Make the front and side panes your responsibility on a set rhythm — a weekly pass with an algae pad, and a blade on glass tanks for the green spots the pleco leaves behind. Cleaning a little and often keeps the film young and soft, which is the stage the pleco can graze, so your scraping and its grazing start working together instead of in separate worlds. Time the scrape just before the water change so what you loosen leaves the tank rather than resettling. The back pane can stay mostly unscraped as the pleco's standing pasture, provided the view from the front stays clean.
Starve the algae at the source
Glass algae that outruns a pleco is usually being fed. Light is the first lever: many tanks run far more hours than the plants need, and trimming the photoperiod is the single most effective algae control there is. The second lever is food — uneaten fish food and a pleco's own generous meals dissolve into the nutrients algae thrive on, so feed the tank's fish what they finish quickly, and feed the pleco at lights-out so its food reaches it rather than the water column. Regular partial water changes then export what is already dissolved. None of this harms the pleco; all of it slows the growth to a pace grazing can match.
Look after the pleco while you fix the glass
A keeper focused on algae sometimes forgets the fish in the middle of it. Plecos need driftwood to rasp — digesting wood fibre is part of how many species process food — and a cave or shaded retreat for the daytime hours. Feed deliberately with sinking wafers and vegetables rather than assuming the glass provides; a pleco in a now-clean tank with no other food is worse off than it was in the green one. Check its belly and activity: a rounded, active fish in a clear tank is the actual goal.
Set the rhythm so it holds
Algae management collapses when it depends on memory — the glass gets scraped when it already looks bad, which is a fortnight too late. A light weekly rhythm of scrape, change and a quick light-and-feeding sanity check keeps growth permanently at the stage where you and the pleco together win easily. Lodge that rhythm in KinsLe Care Teams as recurring duties for the tank and the scraping happens on time, marked off by whoever did it, instead of waiting until the front pane turns green.