You really should be testing your own water. Depending on an LFS is okay for fish only, but you really need to know your parameters and know how much your tank is consuming/producing. You should be keeping a log of test results, test every day or every other day at the same time for a couple weeks to see how much Alk, cal, annals mag your tank is using, and how much nitrate and phosphate it’s producing. Once your tank is stable and the parameters are the predictable, then you can go to once a week. Once your tank is mature and you’ve got more experience, you can probably test once or twice a month. But starting out, you really should be doing it yourself, testing once a week and only being told whether it’s good or bad is meaningless, you don’t know if it’s stable, just that it’s in range (much better to be slightly out of range and stable than in range but fluctuating). At the very least take your water in to the LFS 2-3 times a week (with samples taken at the same time of day), and have them write down the actual parameters. If you want to keep finicky corals (or any corals really), you need to have a more intimate understanding of your tank’s chemistry.