Salvinia minima

Salvinia minima is a small floating fern originating from the American tropics. It has been introduced into the south of the US, where it is considered an invasive aquatic weed.
This floating fern, like other Salvinia species, forms floating mats on the surface of different, mostly stagnant waters.

The floating leaves of S. minima are roundish to broad-oval, have a heart-shaped basis and grow to a length of 1 to 1.5 cm. Under unfavourable conditions they tend to stay smaller, however. The stems branch out and grow to a length of around 10 cm before they break, forming new plants.
The hairs on the leaf surface most frequently form groups of four, and their tips are not connected (magnifying glass). This is an easy way to discern Salvinia minima from S. molesta and other species of the group of plants related to Salvinia auriculata. The hairs on their leaves have an eggwhisk-like form.

Salvinia minima is a very undemanding, nice floating plant for aquaria that grows well under moderate light. Under favourable conditions (nutrient-rich water with a low current) it grows extremely fast and has to be netted out at regular intervals to prevent it from covering the entire water surface. This small round-leaved floating fern looks very interesting in open tanks, and its "roots" (in reality, they are underwater leaves) form great hideaways and feeding grounds for fish fry.