Definitely investing in a solenoid for a pressurized unit, it would be a total fail to have happy plants with a bunch of floating gassed fish, haha
will do, should I get a drop checker for the DIY unit or it's not necessary until a pressurized unit?
I would get a drop checker ASAP. It will give you a good way to see how much co2 is in your tank.
Another diffuser method that's pretty easy is the mist method. It is very efficient way to get the co2 to mix with the water. You place your co2 tub in the intake of a powerhead and this chops up the bubbles really tinny and they fly around the tank.