Vinegar eels...nematode easily maintain and harvested 50/50 mix apple cider vinegar and water.
Swims in upper water column for up to 3-4 days allowing baby fry to hunt them as food source.
$10 for 40mL starter kit
$25 for kit includes vinegar eel culture, harvest bottle, pipettes.
$30 (special $20) 1.5 Liters culture...immediately can harvest and continue culture indefinitely.