I'm guessing the LFS
shop in question is testing for free nitrogen and too ignorant to know the difference. I believe the conversion is to divide by 4.4 or something like that to get actual disolved ppm
values that are meaningfull and toxic to marine life. I also won't bother telling you my opinion of dry test kits. The ones for Nitrate seem to be the worst.
is a septic tank - not an aquarium.
I know a lot of established reef tanks where the owner not only uses city water, but has nitrate levels in the 20-40ppm range as well. These are also your typically large, several years old reef tanks in the 100-300 gallon range that is full of established coral and LR
, but has a sole happy damsel fish swiming around. Nitrate in that case can be relatively high since all the competitors and toxic waste producing microbes have long since starved out. I got money on the tank in question here fitting that description.
This is a far cry from your typical home 70 gallon with half a dozen fish and an army of crabs, snails and shrimp all cranking out loads of ammonia and waste. In that case the byproducts of decomposition are constantly building and need to either be broken down, or diluted with water changes. My advice is to not rely on water changes to reduce nitrate and combat it biologically with a combination of healthy LR
, good tank circulation, a medium sand bed, and a skimmer.