Help a newbie pick a co2 unit

[FishNCash]

Tank is a 40g 36x16x16 on a gorilla rack. I only have about 10" of space on the back of the tank. Which unit would you recommend for a low light Anubias setup.
http://www.monsterfishkeepers.com/forums/showthread.php?p=4325446#post4325446

 

[JamesF]

For a low light anubias setup, I wouldn't recommend one at all.
If anything, get some flourish excel and dose occasionally with that.

 

[JasonG75]

Exactly....no co2 needed for Anubias.

 

[WyldFya]

CO2 is not necessary, but if you want to do co2, I would recommend reaction co2 or a different unit than the one in the link.