Rapid Rooters are the only type I use. The only issue I sometimes are either algae or the root becoming tangled inside the rapid rooter b/c of some of the material is not so giving. To remedy, I make sure the rapid rooter is completely covered when in the system. To help with the seedlings, after a day or 2 after the seed germs. I open the rooter a little to help the roots untangle. Hope this helps.