Bubble Magus C3 vs C3.5

[juanxchoreef]

Hello guys, i have a 80L mixed reef since september and now im moving to a larger system (250L). At the moment i don't use skimmer and i do not have any problem my NO3 are 0-2PPM. Anyways im buying a skimmer next week and my question is what is the difference between c3 and c3.5 bubble magus.

 

[juanxchoreef]

Besides i know having a skimmer will disolve more oxygen in the water