I also go to Fish Town in Flushing and had them detail to me their method. They're methods of keeping Low Nitrates is a little bit different because they are a LFS and can constantly keep up with the tanks. There methods are based on the following -
a. Fishtown does almost daily waterchanges which removes a lot of wastes before they even can become nitrates.
B. They use a gigantic skimmer which helps with the removal of wastes.
Lastly, their display tank does not really have many of the coral that would be affected by even a bit of nitrates. Its mainly LPS and hardier SPS's. Not too many acro's in there.
Just my opinion though. . .
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I think this is a good explanation to this whole topic. I came out of fresh water-- raising discus, where premium water quality is also crucial. But getting to premium is different than in salt. In FW bio balls and bio wheels are king. In SW, they are soooo efficient they create nitrate problems. It took me a while to understand this. Plus, as you stated, lfs stocking is usually much less, they have mammoth equipment and do water changes often. They have issues, but they are different than hours.