Why wafers go in after dark
Plecos and otocinclus are wired for the night shift. Otos spend the day resting on leaves and glass in the shade, and most plecos stay tucked in a cave or under driftwood until the lights go down; only then do they move out and start rasping over surfaces. A wafer dropped at midday lands in front of the wrong audience: tetras, barbs and other day fish pick at it for hours, and what reaches the bottom feeders is the softened remains. Both fish also have the mouths for this work: a pleco's sucker mouth clamps onto a wafer and rasps, and otos work a surface the same way in miniature. Drop the wafers in the last minutes of light or just after lights-out, and the intended eaters find them fresh, while their tankmates are winding down for the night.
Placing pieces so the otos get a share
One whole wafer in one spot feeds one fish. A pleco will settle its body over a wafer and graze it in place, and a group of otocinclus, each smaller than the wafer itself, will not push in beside it. Break the wafer into pieces and set them apart: a piece at the pleco's usual shelter, a piece near the otos' favorite leaves or glass corner, and a spare piece midway if the tank is long. Otos rasp at the wafer's surface rather than biting chunks, so several small pieces give more of them feeding room at once. For a lone pleco, place the piece where he rests rather than in open water, and he will find it within minutes of dark.
How much, and what else they need
As a working guide, one standard wafer covers a single medium pleco for the night, while a group of otos does well on a shared piece, since they are supplementing a day spent grazing algae and biofilm rather than eating a whole meal from the wafer. Plecos, especially the wood-eating kinds, also need driftwood to rasp, and both fish relish blanched zucchini slices weighed down overnight now and then. Whatever is left by morning, wafer fragments or vegetable, comes out: a wafer left to dissolve clouds the water and feeds the very algae you were trying to outsource. Check the bottom in the morning: a wafer grazed down to crumbs across several spots means several mouths found the pieces, not one fish sitting on the whole supply. If whole wafers regularly remain untouched, you are feeding more than the night shift can eat.
Not forgetting the night feed
The after-dark wafer is the easiest feeding in the tank to forget, and the easiest to double when two people both remember it late. It deserves a slot of its own rather than a mental note, with the pieces and their places written down for whoever is on duty. Logging that evening drop in KinsLe Care Teams assigns it to one person and marks it done with a timestamp, so the plecos and otos get their wafers every night, placed in pieces, in the dark, exactly where each of them feeds.