Adding tank to existing tank

[WIReefer]

So I have a frag tank that has 20g volume and a 35 gallon sump I’m adding a 40g breeder to the tank to increase room for frags it’s all plumbed and ready to go will I need to cycle that tank before letting all the water run together?

 

[WIReefer]

Should of worded it better I’ll be adding this 40g breeder to the entire system. So basically plumbing this 40 gallon into that 35 gallon sump