You get instant mashed potatoe from the supermarket. I use porridge---put it through a coffee grinder with a tablespoon of sugar. Cook it in the microwave so it is so thick you have to spread it with a wet spoon, sprinle yeast on top. and add liquid starter (taken off previous culture) and spread it over total media. Worms up the container in 2-3 days and removed with small stiff paint brush from $2 shop. Each culture lasts 4-6 weeks, particularly if you remove the worms each day. Even your adult fish will love them. The media ends up runny and when they no longer climb the container, remove some liquid from the top, store, and re setup.