Swimming Decorator crab

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I built a few of these over the years and was not crazy about any of the designs but this one I made last month works 100%.
My reef now has a nitrate reading of 40 and I figured it would be a good time todesign a new Denitrification device but I had no idea it would work so good and so fast. They usually take a couple of months to fully work but I had it running for a month and I just tested it. Water going in has a nitrate reading of 40 and with just one pass through the device which takes ...

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