Hydrometers read fine, they only give inaccurate readings after being used for a while due to corrosion. Just be sure to rinse it with freshwater after every use and you can get a good long use out of it. That happens to be the same hydrometer i have for my saltwater tanks.
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Current setups: 1800 gallon koi pond, 10 gallon planted, 150 gallon reef, other FOWLR tanks