Without CO2, my PH stays around 7.1 - 7.2 maybe a little higher as best I
can tell with my test kit. My KH before CO2 was staying around 2.

Ideally, you want CO2 to bring your pH down to 6.6 or even 6.4 with that KH.
And you might find it difficult to keep enough CO2 in the tank once you
increase the lighting. With a 75 gallon tank and high light, DIY CO2 isn't
easy.


Leigh

http://www.fortunecity.com/lavender/halloween/881/