The CO2 rabbit hole
CO2 is the single biggest driver of plant growth in a high-tech tank. Cheap regulators are false economy; one fish kill costs more than the price difference.
The Pro-SE line from CO2Art is the current floor for “I trust this on an overnight cycle.” Anything cheaper risks end-of-tank-dump, where a single-stage regulator loses control as the CO₂ cylinder pressure drops and dumps a huge burst into the tank. Fish gasping at the surface in the morning is the usual sign — if you see it, you’re already too late.