Hooking up reactors to sump

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I wanted to hook up two of the Little Fishes reactors to my sump. I wanted one to put Phosban in and the second to put carbon in. Where would I hook these up. Do I tee off of the return piping of the sump, do I add individual powerhead to the sump to feed the reactors. If I do that, what sump section would I put the powerheads in...the overflow or the return?

Thanks alot.