For all of you who are tired of the boring old empty MM2 tundra and pelagic exhibits, I have a solution. I just found out that animals from those two biomes can actually tolerate and enjoy having kelp in their exhibits! Say goodbye to emptyness and hello to kelp forest. I haven't tested any other plants yet; but when I tested the kelp, the animals became happier immediately and started swimming through it. The biome satisfaction also increased when one the animals was only half way satisfied.