Co2

[Red Sea reefer]

Hello every one I wish you all a great day so I read some stuff about co2 but I wanna be sure about what I understand so my questioned is

Where is co2 come from
If I run a bio pellets is it ganna increase or decrease or nothing will happens
Where the co2 will go some chemical equations will help two
Like

H2O + co2 ---- Hco3 + .. ..

Thanks in advance