Mondo grass, or more commonly (in aquaria) Fountain Plant, is actually Ophiopogon japonicus. There is also a dwarf variety, Ophiopogon japonicus var. kyoto that may sometimes be seen under the common name Kyoyo grass.
Hiscock says these two varieties (there are a couple others) are hardy and generally do well in most conditions, though they are not true aquatic plants. These are terrestrial plants often found in gardens, the Mondo Grass of gardners is this genus.
I had this plant many years ago, so far back I cannot remember much about it. Keep an eye on it, if it starts to rot pull it out.