I currently have my tank soft plumbed although it might not be right. It has worked. But now I'm looking to add a uv. Looking how I can modify this or ideas to add a uv sterilizer to it. If I have to replumb it so be it .
Generally you want to run the outlet from your return pump to the UV and then from the UV to the two return outlets to your tank. Soft plumbing is fine - I use the same hose on mine return pump and UV.
I personally would just run a separate pump in your sump, strictly for the UV, pulling from the sump, and returning to the sump. I have always ran my UV units this way so I know exactly how much flow is going through the UV.