I went back to Pacific Aquarium and bought 3 silvertip tetras. Although the tank says “RARE,” silvertips along with other tetras are very common aquarium fish. They’re labeled as rare because they don’t breed in large numbers, but they aren’t rare in the wild. They’re native to the Amazon so the water shouldn’t drop below 70°F. They’re somewhat aggressive, and they school together. They’re omnivores, so regular fish food will be fine but can be given occasional larvae or other small creatures:

The food and water primers (I used spring water, then inserted the prime and stability a few hours before introducing the fish):

Acclimating to the temperature:

Supplies purchased for the filtration system. A water pump, mason jar, airline tubing, ceramic biofilter medium (little ceramic blocks that house bacteria feeding organisms as water travels through) and aquarium sealant caulk which was used to seal the holes I drilled into the lid of the mason jar for the airline tubing:

The pump pumps water into the tube that introduces the water into the bottom of the jar. Then the water rises through the filter medium and back out through an exit tube at the lid: