ok well i am new to the planted aqueriums but i want to run this idea from u guys. my grandfather is a co2 system that was off of a old tap system for a keg will that work for my 29 gallon tank. once he can find it i will post pictures of it and if it will wook what size of co2 bottle will i need
It will work, but you'll need to replace the output valve with a needle valve and another guage that displays the tank's CO2 levels would let you know when its time to replace the CO2.
I don't like that low-side (of the regulator) gauge. You need one that can give you better readings at lower pressures, like a gauge that goes from the zero peg up to 15psi total.
I like the idea of a high-side gauge as well to see when the CO2 tank is nearing an empty state.
Not sure if that regulator will undergo a "low pressure dump" when the CO2 tank gets low. Cheap regulators will typically quickly dump the contents of the pressurized tank when the high side pressure gets below a particular threshold. That could kill your fish.