Pressurized System
CO2 cylinder + regulator + bubble counter + diffuser.
Cost: $150-400 startup. Refill: $15-30 per fill.
Most reliable, controlled, scaleable.
DIY Yeast System
Yeast + sugar + warm water in 2L bottle.
Cost: $5-10 setup. Refill weekly with new yeast/sugar.
Inconsistent flow rate. Best for nano tanks (under 20 gallons).
Liquid Carbon (Excel)
Seachem Flourish Excel — chemical CO2 substitute.
Daily dosing. Less effective than gaseous CO2 but no equipment needed.
Toxic to mosses, vallisneria, and crypts at high doses.
Bubble Rate Math
Aim for 1-2 bubbles per second per 10 gallons.
Test pH drop: should drop 1.0 from off-state to on-state. That's 30ppm CO2.
Drop checker (yellow=high, blue=low, green=OK).
- ✦CO2 on solenoid timer — only during light hours
- ✦Diffuser placement matters — under filter intake distributes CO2 throughout tank
- ✦KH must be 4+ dKH for stable CO2 — buffer if soft water tank