Of course the plant life of any ecosystem is as important as the animals. The plants will root into the substrate and hold in down as well as giving the all-important beneficial bacteria a place to thrive. Plants filter toxins out of the water and turn deadly nitrites into somewhat beneficial nitrates, they suck in waste carbon dioxide and give off live-giving oxygen.
Also, if properly cared for, they look great.
Of course, like everyone, I started with the low-maintenance, low cost variety of aquarium plant, from the popular genus Plasticus Vilis; cheap plastic, often garishly coloured horrors. They make interesting bathroom decorations though.
I did it all, right down to the treasure chest connected to the air pump, you the the one, the air builds up and up goes the lid, the air escapes and it shuts again - har har amusement!
Of course it took time to get the plants right too, let's not speak of the guppy grass incident....
I moved also into the realms of aquaponics and hydroponics, having bought those little plant pots/holders that attach to the aquarium and allow the roots out into that water and those are going very well!