The previous owner of the fishtank mentioned that we have a Neon Green Mushroom.
Our unidentified species looks quite close (although inconclusively similar) to the photo on this page: Ricordea Mushroom – Super Neon Green, so, I’m going to call our guy a Neon Green Mushroom (Ricordea florida) until I learn otherwise…
[...] This is a photo of the Ricordea florida identified in the previous post! [...]
The pictures look more like Green Hairy mushrooms (Genus Rhodactis). Green Ricordia Florida have bubble like protrusions from the disc, and psuedo-tentacles around the fringe.