You absolutely can do this and this is a very common installation. The only thing to consider is that most people's return pumps will be right in line with the algae kill rate of a UV sterilizer but the flow will be too fast for the parasite kill rate. If you want to use the UV for parasite control then you will want to slow down the flow.
So use one of those attachments on the pump pre uv?
If you want to slow down the flow and use your return pump the best way is to use a T fitting and split the flow before the UV with half of the flow through the UV and half going around. You can then use a valve before the UV to further dial down the flow. Because of the T, your flow back to the display will be minimized. The primary difficulty with this setup is you need 2 return nozzles
