Major hydrometer issues

Dear Anna Marie:

I’m sorry to hear your hydrometer has been giving you problems. The swing-arm hydrometers are economical, readily available, and easy to read but they are not very precise at all. In addition to the problem of bubbles sticking onto the pointer and making it appear as if your specific gravity is higher than it actually is, you can on rare occasions get one that has a sticky swingarm that doesn’t pivot as freely as it should.

You might want to try one of the old-fashioned floating hydrometers instead. You just wait until they stop bobbing and then read the specific gravity directly at the meniscus of the water line on the stem of the hydrometer. They are a little trickier to read, particularly if your eyesight isn’t sharp, but they are quite foolproof, inexpensive, and reliable.

Even better, you could invest in a refractometer for very precise readings of the specific gravity. They are pretty easy to use and utterly accurate and precise, but they can be a bit more costly. You don’t need a top-of-the-line unit — just a decent hand-held refractometer suitable for aquarium use.

In any case, Anna Marie, your seahorses should do just fine now that they are acclimated to the aquarium. Seahorses tolerate a wide range of salinities or specific gravity as long as any changes in the specific gravity are reasonably gradual. Your imprecise swing-arm hydrometer will be adequate until you can find a more accurate replacement. I can assure you that your seahorses will not be in any undue danger at all in the meantime.

Best of luck with your new seahorses, Anna Marie!

Respectfully,
Pete Giwojna