Ecology of Underrail

[saladinaladin]

Title. Without sun, where does the biomass get the energy it needs to grow and enable living things to survive? SGS at least does indoor farming, but just what do the fishes in the water eat given photosynthesis (and thus plantlife) isn't readily available?

[HulkOSaurus]

Mosses/Fungi could be the basis of underground life. There are organisms present in the underwater life of Earth as is - those don't need photosynthesis to survive. Various crustaceans are also present. There are a lot of bugs living off bat guano. You could get a hefty amount of protein from roaches. You could actually do a lot with shit underground. Deep oceanic dwellers survive off heat fissures on the bottom. Those same fissures actually form ecosystems. One thing you don't have to worry about underground are seasons - things will be a lot more consistent. 

[ciox]

This at a gigantic scale https://en.wikipedia.org/wiki/Movile_Cave