Refractometer / Hydrometer

[Flaxon-Waxon]

Could hydrometers be off by as much as 2 points? I just got a refractometer and fluid that calibrates to 1026, and measured my tank water and it tested out at 1028! Yikes. My hydrometer read it out between 1025 and 1026... Could this high SG be effecting my fish too?

 

[Mrc8858]

Very much so. Hydrometers have been off by much more then that even. I personally would never use a hydrometer for anything other then when I'm doing a quick check on New mix. If I'm close then out comes the refractometer to fine tune. Imo I give the hydrometer wiggle room of .003 either way which can greatly depend on temp too since instead of only a couple drops having to readjust to room temp its a whole container

 

[Flaxon-Waxon]

So is it the higher the temp the lower the salinity reads?

 

[Mrc8858]

I think that's what it is but I'm not positive on that one. Gonna have to do a little googling or wait for someone else lol

 

[Flaxon-Waxon]

Lol no worries, it's just the whole 3 points of wiggle room that amazes me. Is 1028 detrimental
to the health of the fish?

 

[Mrc8858]

It will shorten their lifespan over a prolonged period of time but if you correct it now and don't see any issues now either I wouldn't be concerned about it.

 

[ccCapt]

Lol no worries, it's just the whole 3 points of wiggle room that amazes me. Is 1028 detrimental
to the health of the fish?

1.028 is OK. It does no harm to the fish or corals. Here's a very good article regarding salinity and temp.
Ron Shimek's Website...Critters
"Coral reefs are generally located in areas that have salinities in the range of 35 ppt to 38 ppt. Most of our corals, and the associated fauna including fishes, will live best at those conditions (Weber and White 1976). Most organisms, even osmoconformers, can survive for brief periods in salinities well outside their normal range. But if maintained for longer period outside of that range they will be stressed and eventually will become so damaged that they will die even if returned to their normal salinity. Higher salinity is slightly more tolerable to these animals than is lower salinity, and adult animals are more able to withstand the extremes than are the juveniles or larvae."

 

[Flaxon-Waxon]

Nice thank you! Also, how often does a refractometer need to be calibrated?

 

[ccCapt]

You don't need to calibrate it very often. Once every month or so is fine. I've had my refractometer for quite a few years and after the initial calibration I think it only drifted out of calibration once, maybe twice.