• Small aquatic plants grown beneath and on the surface of water.Huntstock/Brand X Pictures/Getty Images
  
  Online aquarium resource Aqua Hobby officially defines small aquatic plants as those that reach a mature height and/or spread of less than about 8 inches. The site further divides plants into carpet plants--small plants that reach a height no greater than 4 inches--and standard small plants. Small aquatic plants grow throughout the world, from the United States to Sri Lanka, and can be cultivated in outdoor pond gardens or in indoor aquariums.
  
  

Brazilian Micro Sword

• Brazilian micro sword (Lilaeopsis brasiliensis) is a small aquatic plant native to Central and South America. The grass-like plant grows submersed and emersed in water in its native environments, like Brazil. A submersed plant grows completely below the surface of the water, while an emersed plant grows partially below and partially above the surface of water. Brazilian micro sword reaches a mature height of 1 to 2 1/2 inches and grows in dense patches, or "lawns," in well-lit conditions. Enthusiasts commonly grow the plant in aquariums.
  
  

Whorled Pennywort

• Whorled Pennywort (Hydrocotyle verticillata) is an aquatic plant that is indigenous to the United States. The plant is also known as marsh pennywort, water pennywort, and saltpond pennywort, and is threatened in Massachusetts and considered endangered in New York. Whorled pennywort occurs naturally in wetlands and marshes in New England, the Mid-Atlantic, South, Southwest, lower Midwest, and California and Oregon. Whorled pennywort is a perennial herb listed in the 8 inches and under category by Aqua Hobby. It grows on the surface or banks of water.
  
  

Undulating Crypt

• Undulating crypt (Cryptocorynes undulata) is a species of small aquatic plant that is native to Sri Lanka. The sinisterly named plant grows submersed and emersed in streams and rivers in its island nation home, where it reaches a mature height of 4 to 6 inches. The mature size of undulating crypt is directly proportionate to the amount of light it receives. Though the plant grows in little to no light, it does not reach a mature height of 6 inches unless placed in light-rich environments.