I saw an idea on Reddit where someone turned acrylic boxes into plant containers with suction cups to stick to the walls of their tank. My 45g goldfish tank, lightly planted was rather boring and in need of height to the scape. I couldn't find clear acrylic boxes in town so I settled for the small food containers (used an exacto knife to trim the edges). Each plant is secured to a rock heavier than my largest goldie and each container has a little Flora Max substrate in it. The suction cups are the same ones I've used for the air lines and they stick like glue. I tried to pick plants they might eat as sort of a floating buffet although they haven't touched them yet. Here's the results: They love it!