So! The geothermal vent in Bill's room is an initial success and I'd like to expand it. I'd like the sea cave part to be bigger, and institute a simulated tide cycle, two low tides and two high tides a day. Keep the bottom a mix of rock and sand, with a shallow side that gets exposed during the low tide and a deep end that always has water. I'd like the sandy floor here to get populated with some sort of bobbit-worm type creature that pulls down into the sand and only appears at high tide. The earth variety is acceptable, but I'd also like the water enriched with Yttrium, Samarium, and Promethium, so it should be an animal that can withstand the high heat and metal-enriched water, and I expect we might have to branch out from earth creatures for that.

I'd also like it if the worms concentrated these metals in their bodies, in case Bill decides to snack on them.

At the shallow end of the cave, if you could have a small waterfall dropping down constantly that'd be great.

On the deep side, with the vent, in the upper part of the vent could we get some kind of crustacean population going? Quick-swimming, that can press flat and hide in cracks in the rock, and again concentrating the heavy metals in their bodies.

Where the vent drops... how deep can we make that?