co2 in a sumpped tank

[Rabb.D]

helo,

i was just wondering where is the best place to insert a co2 atomizer in a sumped tank, without compromising the look of crystal clear water, i want to avoid having that fog in the tank or any kind of bubble...

 

[Garuf]

You want a reactor opposed to an atomizer I suspect. A mist is beneficial but I know many who don't like it. As far as possible down the return pipe would probably be the best bet but I suspect this would still give a mist.
I have noticed however some people injecting using regular diffusers straight into the sump but I can't comment on how effective this method actually is.