For sale is a large clump (as in the photo) of beautiful Hydrocotyle sibthorpioides pennywort plant. This plant requires high light intensity to grow. I grow them floating with leaves above the surface of the water and roots submerged in the water. It can also be grown fully submerged if light intensity is strong enough and CO2 is supplied. Growth underwater is very slow and will form small leaves (no larger than 1-1.5cm diameter) compared to growing them floating (>3cm diameter). This plant is quite difficult to get hold of in the UK unless order online or through special order by LFS. I bought it from Tropica through my LFS. It is one of the smaller species of pennywort plants and it is commonly used to create foreground plant and sometimes featured in Takashi Amano’s nature aquarium tanks. In highlight CO2 injected tank, they will create oxygen bubbles or pearling. Because this plant is very buoyant, initial planting is a real challenge! I find it easier to partially bury the stems and roots in the substrate and wait until roots take a firm hold. Once established, it will gradually craw along the substrate.
See my tank setup here and more photos here with very healthy fish and shrimps (all disease-free!!) and I do not add any medications to my tank but I do dose plant fertilizers (mostly from Seachem). It is advisable to rinse and inspect for snails before putting them into your aquarium. Below are photos of the pennywort for sale: | 
