Pond plants provide visual variety in the water and also food for fish, but before installing them, consider the type of pots you'll plant them in. Pots with drainage holes are unacceptable because the drainage hole allows the soil to leech out of pot and stain the water. Instead, choose pots meant to be placed in the water.
Fabric pots are made out of tough cloth with a tight weave. The weave prevents the soil from leeching into the fabric while allowing the nutrients from the water to penetrate to the plant. They are light, and their height can be adjusted by rolling down the top of the pot. The flexible bottom also allows the pot to mould to the bottom of the pond, giving it a more secure seat. Fabric pots are slightly more expensive than other pots and slightly fragile when moved out of the water.
Plastic crates do not rot in the water and are lightweight. To ensure the soil does not leak out of the container, use untreated burlap or landscape fabric to line the bottom of the crate. After that, the pot can be filled with regular topsoil and a layer of gravel and placed in the pond.
No-hole pots are specifically made for water gardens, and there is no drainage hole at the bottom of the pot. The only opening is at the top of a pot, and the soil is weighted down with a layer of gravel to keep it from floating away. They are solid and sturdier than fabric pots, but they can be more prone to tipping over, especially if they are small and overenthusiastic fish are in the pond.