Blackworm starter shipped in a breathing bag
Californian Blackworms are aquatic worms similar to Tubifex, but in my opinion easier to culture.
I cultivate them in small (5-12 litre) boxes, feeding them with dried algae and plants - basically anything organic and decomposing will work. No water flow or filtration is needed, just weekly 50% water changes to keep the water clean. I keep them i same tanks with scuds - they can coexist without any problems.
Package includes a 'ball' of blackworms packaged in a breathing bag, with some food. EU/UK shipping - priority envelope 6.50€.