Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Mondo Grass, Ophiopogon sp. is not an aquatic plant. They do fine in a damp setting, such as roots in the tank, leaves exposed, or in an emersed sump sort of planting, they are good near a pond, or in a shade garden. They gradually spread and become a ground cover, and are especially appreciated in containers and Japanese gardens. They work well around stepping stones, staying low enough to step over, and do not form runners that might trip you. Runners are underground, and not rampant or invasive. The basic green is the most common, but there are related species that are black (just about the darkest plant, it really looks black) and variegated. There are related plants that get a bit larger (Liriope sp). All of these are garden plants, not aquarium plants.
Under water they will sort of hang in there a while, but they are really slowly dying, not thriving.
Similar plants that are better in the tank:
There are some dwarf species of Sag, Vals and Echinodous that will give you that grassy look, and can stay low.
I had some Mondo grass that I placed above the water in a low end brackish tank, and it survived (died slowly). It lasted longer than I thought it would based on the salt level. These are durable little plants!