macrocystis pyrifera / giant kelp
The macrocystis pyrifera, also known as giant kelp, is a fast-growing algae. It is known for getting very big in scale in a short time.
Sensing
This plant can easily be perceived through a glass aquarium or something similar. Due to its size, macrocystis pyrifera can be seen without further tools.
Communication
As the giant kelp is an algae, there is almost no way to communicate with it. One could only change the environment of the plant and wait for a change in its growing behaviour. Besides that, there is a measurable difference in "acoustic behaviour" based on environmental circumstances [1]. In macroscale, they also seem to react to wave exposure [2].
Space
The giant kelp can build large "kelp forests" due to its rapid growth (up to 0.3m per day) and can reach almost 45m length. A glass container with cold water is the appropriate living environment. The algae could build the game space instead of being part of it.
Associations
The structure of their leaves could be used as a long-term randomizer or a biologically changing game environment.
Ethics/ Living Conditions
Macrocystis pyrifera thrives in cool water with a temperature below 21 °C. The ground should be rocky and build possible "anchors" for the plant. They reproduce theirselves by spawning eggs, which later grow to new adult plants.
Logistics
Mostly sold as powdered food; seems difficult to buy living instances or eggs.