Developing an Assassin Snail Aquarium

This is my basic 20 gallon set up with more to be added soon! My substrate is 35 plant based with floating Java Fern with the roots brushing the gravel. The Java Fern tends to grow quickly and large so I am sticking with it as the background plant for now. I also have a Seapora 30 sponge filter with a capable air pump. You will note the Morimo "Moss" balls floating at the top?

To assist in the tank cycling I purchased 6 "Fathead" Minnows. I have lost one that was the runt of the group but the rest appear to be doing well. These minnows were slated to be used as feeders.