Planted Tank Guru
Join Date: Jul 2010
Location: British Columbia, Canada
Not to disagree with any of the above posts, but since you are getting very small juvie discus whose immune systems are not yet well developed, you would be taking far less risk by not running CO2 at all for the next couple of months until they grow out some, preferably to over 3 +".
The use of CO2 could readily produce some unfavorable pH swings, which is a serious no-no, especially for very young discus.
Since you are running CO2 now, I'm assuming your tank is fairly heavily planted, which is also a bit problematic from the standpoint of being able to adopt a good tank cleansing routine, to produce & maintain the high water quality & conditions those young discus really need, until they grow out some more.
Do yourself a favor, and place all your focus on keeping those discus healthy & thriving, even if your plants suffer somewhat in the meantime. Your emphasis should naturally be on the expensive fish.
And I would also suggest you consider adding 2 more discus when you can, so as to maintain better social compatability, and lessen pecking order/aggression issues which could develop soon.
Hope this helps you.