If you have a preformed pond, or one with a butyl liner, you will need something to plant into. You could use hessian possibly, or our preplanted coir products, but failing that we offer these planters.
These fine mesh planters are ideal insofar as you won't need to line them, but the mesh isn't so fine that it doesn't allow the flow of water through them. This allows oxygen and nutrients to get to the plants.
Fill them with a low nutrient planting medium like subsoil - you don't have to use specialist aquatic soil. If you don't have subsoil you can mix topsoil with a horticultural sand, and top off with gravel to stop the whole lot floating off.
The sizes we stock are ideal for the native aquatic plants we sell. If you're buying our 42 plant pond collection reckon on planting 20 odd plants in the baskets, as opposed to on the pond edges. You typically want the top of the basket to be at the water level or 5cm or so below.
11cm x 11cm X 11cm (1 litre): one plant
28cm x 28cm x 18cm (10 litres): four plants
45cm long kidney shape X 15cm deep (8 litres): three plants