well you need to keep that cube moist enough and below it moist enough so that when roots break they can grow down into the res. How often depends on temp and humidity. after they establish their roots in the res you stop the top feeding altogether
Rule #1 is ask first then do something...
That saves endless grief
When you stand at the precipice and are about to jump along with your plants...stop, think, ask, then act ONLY if you are pretty sure. NOT doing something is often correct.