I don't know if you've searched this forum for old threads on this subject or not, but I'll attach a link for you just in case.

Here is a link that might be useful: click here for great information

Spring, summer, and fall maintenance is easy for water garden containers. The customers at the garden maintenance north shore are always in need of the the maintenance for the container gardens. Simply add water to keep it at the proper level and feed the plants and fish as necessary. Occasionally, the water may turn tea-colored though the decay of leaves or the pot may fill with unsightly debris. Empty the container, rinse it clean, and refill as quickly as possible to prevent the plants from drying out. Do not scrub the container clean as this will remove too many beneficial bacteria growing on the container's surfaces.

Winter maintenance depends on the type of plants, type of container, and the climate of the container's location.It should be a fifth of the total cost of the garden