Amazon21 has mentioned my thinking correctly, so enough said. However, if by "needing" CO2 you are meaning to lower the pH, I would suggest a better method would be to dilute the tap water (which reduces hardness proportionally) and letting the pH fall naturally. That way, no CO2 is needed. One less thing to go wrong; as another experienced (with CO2, unlike me) member mentioned in another thread this week, killing off fish with CO happens. And Discus
being sensitive, it is one less thing to worry about.
I would not keep neon with Discus
, due to different temperature requirements. Discus
need the warm of 82F+, neons will quickly burn out above 77-78F. Cardinal Tetra
are better, and maybe some Brilliant Rummy Nose Tetra
with them [click on shaded names to see that profile]. Both manage fine at the warm temperature and naturally occur with Discus
in the wild so a good match. And these fish also do not like light; cardinals have what Baensch called a light phobia. So do most forest fish actually. You might want to have a read of my article on light and how it affects fish, here: Lighting: How It Affects Freshwater Fish