i believe the brand is hydor not red sea, the system came with both the co2 unit and diffuser w/all the connections and tubing i needed... what size light do you think would be ideal for my size tank?WyldFya;1014763; said:Reaction co2 is using one of many different reactions to get co2 to be produced. Generally yeast and sugar is used. Since you paid $60 for your co2 unit (not the diffuser) I'm guessing you got the Red Sea unit, which is overprice IMO.