First, there are the sharks. I made this organism. They swim up to eat the sticky seaweed. Their nutrient priorities are set up in a way that makes them swim up. I don't fully understand it, it just evolved that way.
Then you have the sticky seaweed. I made this organism. First, they start out as an egg, then they turn into a simple swimmer with a photocyte head, and the flaggelocyte has nutrient priority. This causes them to swim up. They swim up to the top where their head turns into a glueocyte and a photocyte, and they stick to the top and the photocyte makes eggs. They regularly fall off the top edge in huge chunks which feeds the sharks.
You also have the tuna fish. I think these fish evolved from the sticky seaweed because their tail color is the same. They are just a simple swimmer, and the flaggelocyte has nutrient priority. This allows it to swim up. From what I have observed, the purple head produces one egg and turns the head yellow. The yellow head makes one egg then falls off. I could intervene and improve this animal, but since it evolved 100% on its own I figure I'll let it stay as it is.
Then you have the whales. I made this organism. They are like sharks, except they have a phagocyte for a head. Sharks cannot eat them, although sharks can eat baby whales.
Lastly, you have the whale sharks. I call them this because they are a mixture of a whale and a shark. They can't swim as high as sharks, but they still swim up. Young whale sharks look like sharks. I made this organism.
I have let this substrate run for over 50,000 in-game hours to get these results. If you want to create an ecosystem with more than 2 or 3 species, I do believe that you must create multiple niches for them to live in, which can be done using gravity, density, and light.
Substrate: https://www.dropbox.com/s/q0mw977i2bhwr ... trate?dl=0