Bacopa monnieri 'Compact' is a form of the well-known Indian pennywort or Water hyssop that is still relatively new to the aquarium hobby. Although the plant also forms long, upright shoots, it is easier to shape into a compact, branched bush than 'normal' Bacopa monnieri. The plant also develops a more elongated leaf shape under water. With plenty of light, almost creeping stems can develop in addition to upright ones.
The submerged shoots, up to over 30 cm long, have about 2.5 cm long, 8 mm wide, somewhat fleshy leaves on a 2.5 mm thick stem. The internodes (distances between the stem nodes) are about 1 to 2.4 cm long. In the terrestrial (emersed) form, the shoots grow prostrate and take root at the nodes. 
For some time now, this Bacopa has also been sold under the false name "Hedyotis salzmannii", but true Hedyotis salzmannii is a completely different plant that is very rare in the aquarium hobby.
The Compact water hyssop is just as undemanding as normal Bacopa monnieri. It is suitable for aquariums without CO2 supply and with rather hard water, but its growth is greatly promoted by CO2 addition and complete macro- and micronutrient supply via the water column. The plant grows in a wide temperature range of about 15 - 30 °C, about 18 - 28 °C is optimal. It has a moderate light requirement and grows even in the shade of other plants, but with strong lighting it shows the most beautiful, compact growth. Branching and low growth is also achieved by cutting the vertical stems.
Bacopa monnieri 'Compact' is versatile. With appropriate pruning it can be shaped into a taller carpet or low bush in the mid to foreground. You can also grow a taller stand, at least about 30 cm high. In the emersed form, this Bacopa can be used for paludariums and wabi-kusa. It then forms a carpet with its prostrate, branched shoots and you can count on its pale violet flowers.