Not mesh, though you could stitch up a couple from tulle net or other material.
I have used the plastic pots and pond pots. Also am using terra cotta clay pots to hold a few plants in the pond. They have some stones over the top to help keep the soil in. But still problematic because I immediately knocked one over and soil went floating and spilled out and made a huge mess. That was just in the pond too, in the tank I would have died an early death.
I did well just floating plants with some plant weights so they stayed down at the bottom, and upright, directionally, like they were planted but they weren't.
