I was wonder how the good aquascapers cover their ground in their aquariums

Question

and what kind of plant that super small almost kat nip type grass is

Answer 1

You can buy some really good substrates for plants, like Eco-Complete, laterite or fluorite.  I've also heard that some of the pro aquascapers use an inch or two of soil covered with sand or gravel to keep the soil from floating up and fouling the tank water.  You have to make sure the soil is straight sterilized soil without any additives such as fertiliazers, as most of those include nitrates which will mess with your water conditions.  The article below talks about "Supersoil" being used for planted tanks.  A soil/sand/gravel combo grows great aquatic plants.  They also recommend the use of Malaysian Trumpet snails to keep the plant roots aerated and help the water circulate through the substrate.

One of the more common ground covers used that looks like short grass in tanks is dwarf hair grass.  Is that what you mean?

Answer 2

There's Dwarf Hairgrass (near the back in this picture):

http://images3.fotop.net/albums3/justinl...

Glossostigma Elatinoides: http://www.geocities.jp/goleshiiriin/pla...

Hemianthus Callitrichoides: http://www.plantacquari.it/images/piante...

And Marselia species:

http://www.floridadriftwood.com/images/p...

http://www.darkwhite.info/images/plants/...

I personally use Marselia Quadrifolia: http://i7.photobucket.com/albums/y300/ry...

HC, Glosso, and Dwarf Hairgrass aren't the easiest plants to grow, they need high light, good levels of CO2, and adequate fertilization. Here's some great forums with people who can help you with these plants: http://www.fishlesscycling.com/forum/

http://www.plantedtank.net/forums/

http://www.aquaticplantcentral.com/forum...

E-mail me for any questions!