not sure if bryopsis algae or not based on the picture, but if it is, it's a Bit#h. Pretty sure your LFS doesn't have a clue on what they are telling you. It appears your only running an HOB and no skimmer? You might get away with that if your running a large amount of Live Rock and ALOT of recirculation flow within the tank. An HOB will not turn over enough.
You guys need to first get a system setup that is capable of growing SPS or LPS if that is what you what to do, then add livestock. Get the sump/refugium set up and running. Get your nutrient levels acceptable (concentrate on nitrates and phosphates first, get them under control, then start looking at others. If your readings approach zero and you still have rampant algae, your getting readings of "false positives" meaning that the algae is consuming available nutrients and still giving you a low reading. Trust me, if you have algae, it NEEDS these two components). Slow down and get your system able to handle what you want to grow. You will never be able to sustain an SPS tank using a HOB filter, and if the LFS says so, tell them they are Full of you know what. This is all about trying to maintain a "balance" of trace elements, nutrients, and light. Excess in any one usually will give you signals (much like the algae is giving you). Even when you get it al in sync, there are events that are unexplainable (bacterial, contaminates, etc.).
Best of luck, but unless you conquer the algae, you won't progress much in this "sport"
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