While the idea of repurposing a regular urban planter box for aquatic plants is appealing, it is generally not recommended. The fundamental needs of aquatic plants differ drastically from terrestrial ones. A standard planter is designed for optimal drainage, allowing excess water to escape to prevent root rot. Aquatic plants, however, require their roots and crown to be consistently submerged or in saturated soil. Using a regular planter would cause water to leak out rapidly, failing to maintain the necessary water level.
For successful aquatic gardening, you need a specialized aquatic planter or container. These are typically made from non-porous materials like plastic, fiberglass, or glazed ceramic, and they lack drainage holes. This design creates a water-tight environment to keep roots submerged. Some aquatic planters even have built-in lattice or fabric to contain soil while allowing water to circulate through the roots.
If you attempt to modify a regular planter, you must permanently seal all drainage holes with a waterproof sealant. You must also ensure the material itself is non-porous; unsealed terracotta or wood will leak and may introduce harmful chemicals into the water. Ultimately, investing in a proper aquatic container ensures healthier plants, clearer water, and a more stable ecosystem for your miniature water garden.