not op but here's the day I bought, works great

Comes with everything you need except baking soda and citric acid

Oh duh I see now. For my 29 gallon aquarium I use a 2.4L tank takes 400g. I cheat a bit and add more and get great pressure. Using their recommendations seems to generate minimal pressure so I can see why you get so few days? See a link to my co2 system below

Clscea 2.4L Aquarium CO2... https://www.amazon.com/dp/B08YJ8T2F4?ref=ppx_pop_mob_ap_share