Plants

Hi

I regard myself as very new to to keeping fish. I enjoy it very much and
have read up a lot about the various species and tank setups I monitor the
water closely. Nitrite is somewhat high - but not dangerous. I fancy real
plants, but have been rather unsucessful with them. I am reading a lot
about these C02 defuser equipment, but I have never seen one in my life and
have no idea how it really works and how it works. My questions:

1. Isn't the CO2 dangerous for the fish?
2. Does it really make a big difference? Isn't their an alternative?
3 What is the cost of these things?
4 How does it look?
5 Which do you recommend.

Newbie signing off ;-)

Regards
Sparky