Actually I don't plan on doing injection. At least not at the start.

Do not go over 3 wpg without CO2 injection. In fact, staying close to 2 wpg
would be better. Just leave some of your lights off until you can get a CO2
system set up. (Compressed would be best for a tank as large as 75 gallons.)

Too much light without CO2 injection will be algae hell. Worse, it can cause
pH swings extreme enough to kill your fish.


Leigh

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