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@BackbayReef
SCRM😎 Cool Kids🧠Reef Guru
Joined May 2026265 posts1,033 pts★5.0(2)
🔧 Build Contributor
Water Chemistry·Sep 23·👁 102#1

What’s your salinity?

I’ve been trusting the Apex’s salinity probe and thought it l’s been 35ppt (1.026SG). Well, per the last ICP test, it was really 33ppt(1.024SG) for months! That means all the other elements were also low. I’ve recalibrated and add to my monthly checklist! Also, have a secondary source (e.g Milwaukee digital refractometer) to validate. @dooly suggested getting a TM hydrometer as a more reliable source. What level of salinity do you run and how you test & calibrate salinity?

— /yolo

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Replies (12)

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  1. @janiners305
    SCRM😎 Cool Kids🌸Polyp Whisperer
    Joined Aug 202672 posts284 pts📍 Glendora, CA
    🔧 Build Contributor
    Sep 23#2
    We had the same thing happen. Thought we were running 1.026, turns out it is 1.024 also lol. We have a Vee Gee refractometer, and the TM hydrometer as well. We have a Hanna salinity checker in the cabinet, but have never opened it to use since we have the Vee Gee. Just keeping as a backup, because you never know.
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— 105 gallon mixed reef - SPS/Torch/Goni

  • @Drexl
    SCRM😎 Cool Kids⚡SPS Slinger
    Joined Aug 202688 posts364 pts📍 Porter Ranch, CA
    Sep 24#3
    I have no confidence in salinity probes, too many issues to make them reliable for true readings. I use two trusted instruments for testing salinity, glass hydrometer (Tropic Marin) and D/D Ocean refractometer. One of the best refracometers is the VeeGee STX-3. You can also make your own calibration solution for a refractometer with table salt and RO, but requires a scale with 1/100 accuracy. I keep salinity at 35ppt to keep it simple and that's what every test kit is based off of, so if you're salinity is off, then your test results are off.

    — Clams and acros

  • @wsoldier
    😎 Cool Kids⛰️Aquascaper
    Joined Aug 202632 posts140 pts📍 Burbank, CA
    Sep 24#4
    I threw out my apex salinity probe the first week. Refractometer and the hanna hand checker for relative sampling (ie tank and mixing container). I keep my tanks at 1.026.
  • @ktran
    SCRM😎 Cool Kids⚡SPS Slinger
    Joined May 2026161 posts683 pts★5.0(1)📍 Tustin, CA
    🔧 Build Contributor
    Sep 24#5
    I'm impatient so I use the Hanna checker. Love it so far

    — Always keeping it simple

  • @Ndrwater
    SCRM😎 Cool Kids⚡SPS Slinger
    Joined Aug 202687 posts395 pts
    Sep 24#6
    I use a BRS refractometer. Works great ... As long as I calibrate with the solution regularly. I also have the big ass floaty glass one too. Its always spot on, but kind of a PIA to use. Oh... And 35ppt or 1.026

    — Yup....

  • @Ndrwater
    SCRM😎 Cool Kids⚡SPS Slinger
    Joined Aug 202687 posts395 pts
    Sep 25#7
    @ktran wrote: I'm impatient so I use the Hanna checker. Love it so far
    I might need one of those...

    — Yup....

  • @ktran
    SCRM😎 Cool Kids⚡SPS Slinger
    Joined May 2026161 posts683 pts★5.0(1)📍 Tustin, CA
    🔧 Build Contributor
    Sep 26#8
    @Ndrwater wrote: I might need one of those...
    They are 100% worth it

    — Always keeping it simple

  • @BackbayReef
    SCRM😎 Cool Kids🧠Reef GuruOP
    Joined May 2026265 posts1,033 pts★5.0(2)
    🔧 Build Contributor
    Sep 30#9
    The Apex salinity probe is drifting again — my tank is at 35ppt/1.026SG (verified with separate probes) yet the Apex is jumping all of the map. I even calibrated last week - so disappointing.

    — /yolo

  • @Ndrwater
    SCRM😎 Cool Kids⚡SPS Slinger
    Joined Aug 202687 posts395 pts
    Sep 30· edited Wed, Sep 30 · 6:53 PM#10
    Saw a thing yesterday from VCA for salinity probes. Supposedly keeps things from drifting due to bubbles and the like. Let me see if I can find a link.. vividcreativeaquatics.com/shop/sps-kit-the-sali…

    — Yup....

  • @ATAquariums
    😎 Cool Kids⛰️Aquascaper
    Joined May 202613 posts102 pts★5.0(1)📍 Santa ana, CA
    Sep 30#11
    I'll run from 1.024-1.026

    — Lets try and help everyone out. At one time you didn't know better either.

  • @BackbayReef
    SCRM😎 Cool Kids🧠Reef GuruOP
    Joined May 2026265 posts1,033 pts★5.0(2)
    🔧 Build Contributor
    Sep 30#12
    @ATAquariums wrote: I'll run from 1.024-1.026
    I’m crazy - it needs to run at 1.026 or I’ll freak out! lol

    — /yolo

  • @BackbayReef
    SCRM😎 Cool Kids🧠Reef GuruOP
    Joined May 2026265 posts1,033 pts★5.0(2)
    🔧 Build Contributor
    Sep 30#13
    @Ndrwater wrote: Saw a thing yesterday from VCA for salinity probes. Supposedly keeps things from drifting due to bubbles and the like. Let me see if I can find a link..
    My salinity probe is sitting in a calm area of the sump, not aware of bubbles & turbulence…

    — /yolo

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