Two cultures that work on opposite principles
Microworms and daphnia are both classic home cultures, but they could hardly be more different to run. Microworms are microscopic nematodes that live in a damp paste on the floor of a small tub and feed fry too small for anything larger; the culture needs no light, no air pump and almost no space. Daphnia are tiny water fleas that swim free in open water, filter-feeding on algae and bacteria, and they suit larger fry, juveniles and adult fish that hunt moving prey. Starting both gives you a size ladder at home: microworms for the first days of a fry's life, daphnia as mouths grow. Each culture needs a small starter to begin — microworm starters and daphnia starters are traded constantly between local fishkeepers and clubs — and each rewards a steady, boring routine far more than any special equipment.
Running a microworm tub
Cook plain oatmeal into a thick paste, let it cool, and spread it about a centimetre deep in a small lidded plastic tub. Stir in a pinch of dried yeast and your starter culture, press the lid on with a few pin-holes or a cloth vent, and keep the tub at room temperature. Within days the surface glistens and worms climb the walls above the paste line — that climb is your harvest. Wipe them off with a fingertip, a cotton bud or the edge of a card and swish the wipe in the fry tank; the worms sink slowly and wriggle, which is exactly what triggers tiny fry to strike. Feed the culture a fresh pinch of yeast every few days, and start a daughter tub from the old one every couple of weeks, because an ageing culture turns sour and vinegary and production falls off before it fails outright.
Raising daphnia in a bucket
Daphnia want volume and light instead of paste: a bucket or spare tank of dechlorinated water, set somewhere bright, with the water kept faintly green. Add your starter, then feed the culture little and often — a dusting of yeast dissolved in water, spirulina powder, or green water from a sunlit jar — stopping whenever the water stops clearing between feeds, since overfeeding is what crashes daphnia cultures. A gentle air stone keeps the water moving without battering the swimmers. Harvest with a fine net or by scooping a jugful and straining it, and pour the culture water back, topping up with aged water as you go. A healthy culture pulses: numbers boom, you harvest hard, they recover. If the water turns milky and smells, you have fed too much — halve the feeding, change part of the water, and let the survivors rebuild.
Feeding your fish and keeping cultures alive
Rinse or strain harvested food so you are not pouring culture water — rich in bacteria and waste — into the fry tank along with the worms or daphnia. Offer only what the fish clear in a few minutes; uneaten daphnia can live in the tank until eaten, but dead microworms foul a fry tank quickly, so wipe modestly and often rather than flooding the tank once. The real secret to home cultures is redundancy: keep two tubs and, if you can, two buckets, staggered by a week, so a crash is an inconvenience rather than an emergency with hungry fry. Cultures fail silently when their routine slips, so put the yeast feeds, the harvest days and the fortnightly re-culture onto KinsLe's Care Teams schedule for the tank, where each small job is ticked off with a timestamp and nothing depends on memory.