Get some locally. Believe it or not you can rinse it under running water from your sink. I got a hold of some chaeto that I knew for a fact had aptasia and flatworms in it. I rinsed it under the sink, picked out exemplary strands and I was done. There is no aptasia or saltwater flatworms that I know of that can take nice fresh chlorinated water and live to tell the tale. You’re basically disinfecting it. Your algae doesn’t care if it’s sink water for a few minutes. It doesn’t have gills. There is nothing in my tank that I don’t want in it.