What's the other alternative of algae water?

You can buy Copepod cultures at your LFS or online. Almost the same process, but you'll want to maintain your culture with aged aquarium water (after a water change) or rain water. Put the container you chose to use under direct light for 48-72 hours for bacteria and phytoplankton to grow for copepods to eat and you're set. Or, if you have a spacious, well-off tank, your fry can survive off of the ecosystem of the tank. I've left fry in the same tank as they were born, yes a couple were eaten, and they've grown into full adults in a 10 gallon tank.