If you were to buy one for a reef tank, you'd want the low range model. If phosphates in a reef tank are > 2.5 ppm, it's likely to be pretty obvious and would be seen as a large algal bloom. Also, having a resolution of 0.01 ppm is much more appropriate than 0.1 ppm for reef applications.
Personally, I can think of better ways to spend $200+ (unit, extra reagent, spare cuvet / cap). To me, it's really a specialty item -- not something for the average reefkeeper. I've used similar instruments in labs in the past (and more complicated ones) to measure nutrient levels and I still wouldn't spend my money one, nor do I think the average reefkeeper has the time or patience to really use such an instrument properly. Any fingerprint, scratch, moisture, dust, etc. on the outside of the testing cuvet can significantly throw off results. I just don't think it's a pratical purchase for most hobbyists.
