Putting Real Plants In Aquariums

[kent]

i never used CO2 since i first set up my tank 2 months ago..they looked fine and growing but the leaves are getting all ugly..so i measured my CO2 levels and found out it's below normal so i started using one...il see if there's any improvement.

 

[SilverDollar_03]

where could you get stuff to measure co2? becuase i dont ever see anything like that in my petsmart. and i know you can calculate it with pH and KH too, but i dont know of anything to measure KH either!