The hidden ecosystem inside every aquarium.

Why microfauna matter

Every established aquarium is a tiny ecosystem, and microfauna are its foundation. They graze biofilm and algae, break down waste and uneaten food, and convert detritus into a living food source for your fish and fry. A tank with a healthy microfauna population is more stable, more self-sufficient, and far better at raising fry than a sterile one.

For breeders, microfauna are not a curiosity — they are infrastructure. The reason a planted, “dirty” fry tank out-performs a bare, scrubbed one is microfauna: infusoria and rotifers feed the smallest fry around the clock, while cultured live foods like microworms, daphnia, and scuds drive the growth that decides survival rates. See the full feeding system in Best Live Food for Betta Fry.

The flip side is identification. When something unexpected appears — tiny white worms on the glass, jerky specks in the water column, a thread waving from the substrate — most keepers panic and reach for chemicals. Usually that is the wrong move. The majority of microfauna are harmless or beneficial, and the few real pests are controlled by addressing their cause, not by nuking the tank. Each entry below tells you whether to leave it, culture it, or control it.