Prune off any leaves that have emerged above the water at a leaf joint. If desired, leave some of the emergent leaves in place. Discard the emergent cuttings or plant them in a tropical terrarium. If you are growing this as a horizontal floating plant, cut back the stem at a leaf joint to the desired length.
Cut back stems beneath the water to the desired depth at a leaf joint. You can cut the stems back by up to 50 percent. Plant the subsurface cuttings in the aquarium substrate if you want more pennyworts. Otherwise, discard the cuttings.
Prune back any lateral shoots. Leave only the shoots that grow vertically. Alternatively, if you want a horizontal plant, prune the vertical shoots and leave the horizontal ones in place. Prune this plant monthly or more often if needed.