A cold-water fish you can keep without a heater. Above 26°C it weakens quickly, making it hard to keep with tropical fish.
The largest group where none died in 90 days. Tap water · black sand · bacteria starter on day 1 · fish added on day 10 · 25% weekly water changes.
Run a 60 cm standard tank with 13 yourself →The same rules the engine uses for tankmates.
No eating or bullying either way, with plenty of overlap in temperature and pH. Fish that swim at a different level come first.
The numbers on this page come from the Water Kiwoogi simulator model; real tanks can differ.