I have been growing for years and usually I use 5/16 hole and for a 3 gallon bucket, typically about 12-16 holes spaces out in a diamond pattern. You have to be concerned with fungus gnats getting to them. So stuff the holes with polyfil until they are ready to fruit. I pop the polyfil out and wash it really well, let it dry and use it again unless it has trich or penicillium growing on it.