That's a pretty vauge post.Can't say if it's worth it unless we know what kind it is.Also can't say if your tank needs one if we don't know what you have....But,most new UV's can be bought for around 150-200 bucks.So unless this is in LIKE NEW condition,I would just buy a new one.Plus a used unit has NO WARRANTY.Also,what about the bulb???These need to be replaced every year.So you need to figure in the cost of a new one...