I use these low budget CO2 systems in most of my aquascapes!
they are super cheap, easy to make and work great. This system is great if you are new to CO2
Few downsides:
1. Can't be switched off
2. Needs a refill after 4-5 weeks
3. CO2 levels can't be regulated.
The recipe:
250 grams of sugar
300 grams of water
3 sheets of gelatin
2 grams of yeast
MAKE SURE YOU SUBSCRIBE TO MY CHANNEL: http://bit.ly/2Tm5CpS
if you don't like diy CO2 here's a link to some pro stuff
USE CODE ''AMSTERDAM'' FOR 10% OFF CO2 EQUIPMENT: http://bit.ly/38apvpy