testing water in the bag once you take the specimen home is like testing toilet water after you dump in it.
yes lfs are pretty well known for having high NO3 but not all. when i worked at one about 2 years ago all of our tanks except live rock tank were about 20. the coral tanks were heavily filtered and "over skimmed". i trained the owners on owning and maintaining these systems as they were still incorporating the same practice as when they opened in the mid 80's. all fish tanks were on same system as coral tanks and frag tanks. i separated them, grabbed more stuff off retail shelves and set them up individually. next thing you know...we were fragging our retail corals, coloration was great, awesome growth etc.....2 years later they have completely exploded in the salt department and have a great name in the local area.
now all this was not due to "ME". all i did was plant the seed and fertilize it. i stopped working there shortly after that as i took a transfer out of state but about a month ago when i stopped by they actually thanked me! i was blown away!