I used to keep tropical aquariums. 10 gallon, 30 gallon, lots of different danios, tetras, and the like. I had a knack; some of my fish lived 3-5 years. Fishkeeping is half chemistry and half devotion. I changed their water faithfully and I kept the water chemicals balanced–things like the pH and ammonia levels and so on. Fish are incredibly sensitive to their environment; using soap on the aquarium might kill them all, for example.

My last aquarium in Phoenix was the biggest I’d ever kept. In Phoenix, I didn’t have a neighbor to feed the fish when I was away. I didn’t travel much, and usually it was just a weekend. For three days, I could let the fish be hungry; it wouldn’t hurt them.

But one time, I needed to be gone for eight days. I decided to try one of those vacation feeders. They gradually release food into the water so the fish can eat for a week. I went on my vacation, not too worried.

I returned to find 10 dead fish and a whole bunch of sick ones. Turns out the vacation feeders aren’t all they’re cracked up to be. It ruined the chemical balance in my water and killed a bunch of fish. A great fish tragedy indeed. Many eulogies were spoken over the toilet.

But here’s the kicker–no matter what I did to that tank afterwards, no matter what treatments I used or how I changed the water… I never got that tank healthy again. I kept losing fish. Randomly and inexplicably. They became ghosts in a haunted mansion. I had to abandon that tank.

Which brings me to my gloomy thought. Even if technology advances dramatically–even if we find a way to remove pollutants from the air or clean the oceans or cool the planet back down–it may never be able to sustain healthy humans again.