you said you were given a uv filter, is it a straight uv or a filter with an inbuilt uv ? pros- if set up right it will kill of any bad bateria that got passed the filter.Cons- it has to be put on the return side of the filter so you will loose some head pressure and it will take a bit to get the flow just right. But since you got it given to you I would give it a go, I have one on my fresh water sump and I think it dose a good job. I hope this helps answer your question