Djplus1 September 8, 2012 Share September 8, 2012 I was wondering if there was any difference in where you took salt measurements from. For instance, I just did a water change in my 72g bowfront. I added freshly mixed saltwater to the sump. After around 20 minutes, I took a measurement with my refractometer in the sump which got a reading of 36 ish and then I decided to take a measurement from the display (around an inch from the top of the tank) and that reading was 31ish. Which number is more accurate? Neither... perhaps if it takes a while to mix together completely? Which location should I be taking my measurement from? Link to comment Share on other sites More sharing options...
flooddc September 8, 2012 Share September 8, 2012 Make sure you refractometer is calibrated. What's was the reading on the "freshly mixed saltwater"? When you add new SW, you want to keep it the same or close to your SW reading. Link to comment Share on other sites More sharing options...
Djplus1 September 8, 2012 Author Share September 8, 2012 Make sure you refractometer is calibrated. What's was the reading on the "freshly mixed saltwater"? When you add new SW, you want to keep it the same or close to your SW reading. Funny you ask. I had to double up salt on the last 5 gallons to read about 60 to raise my salt level as it was pretty low, as it was at about 30. I just have a couple of hermits and a couple snails in and was trying to add a few more today, so wanted to make sure salt was up. The refractometer is calibrated between each use, BTW. Link to comment Share on other sites More sharing options...
Djplus1 September 8, 2012 Author Share September 8, 2012 Funny you ask. I had to double up salt on the last 5 gallons to read about 60 to raise my salt level as it was pretty low, as it was at about 30. I just have a couple of hermits and a couple snails in and was trying to add a few more today, so wanted to make sure salt was up. The refractometer is calibrated between each use, BTW. Oh also, what about the display vs sump measurement? Is there a preferred way? Link to comment Share on other sites More sharing options...
STEVE September 8, 2012 Share September 8, 2012 Just curious...what do you folks use to calibrate your refractometers? Link to comment Share on other sites More sharing options...
Djplus1 September 8, 2012 Author Share September 8, 2012 Just curious...what do you folks use to calibrate your refractometers? Instructions say to use RO/DI water and use adjustment screw to null. Honestly, it hasn't changed since I first set it up, but better safe than sorry I guess. Link to comment Share on other sites More sharing options...
STEVE September 8, 2012 Share September 8, 2012 Mine either...thats why I was asking Link to comment Share on other sites More sharing options...
flooddc September 8, 2012 Share September 8, 2012 (edited) Oh also, what about the display vs sump measurement? Is there a preferred way? Both DT and Sump should have the same reading. I don't see any reason why you get different readings. You use a droplet right? Only, thing I can think of is droplet. Maybe be it contain salt residue that could give you inaccurate reading. Just curious...what do you folks use to calibrate your refractometers? I use Refrac. calibration solution. But I read that you can use RODI water too. Edited September 8, 2012 by flooddc Link to comment Share on other sites More sharing options...
Glenn September 9, 2012 Share September 9, 2012 I always wait AT LEAST an hour to check the salinity, that gives all the water time to mix together. I don't think I've ever checked the salinity of the sump. Since the fish and corals are all in the DT, that's where I pull my droplet. I will take about 4-5 pulls of water in the "syringe" and push them all back into the tank. Then I take a new syringe full, let a few droplets out and finally add two droplets to the refractometer to get my reading. Link to comment Share on other sites More sharing options...
smallreef September 9, 2012 Share September 9, 2012 I use refract solution to calibrate, then do my test with a dropper, then rinse my dropper with my waste water Link to comment Share on other sites More sharing options...
Djplus1 September 10, 2012 Author Share September 10, 2012 Thanks for the answers everyone. It did eventually level out to read the same in each location. I assume that since I added the new salt water to the tank it just took awhile to leave the sump completely, thus giving me a higher reading. Link to comment Share on other sites More sharing options...
hypertech September 11, 2012 Share September 11, 2012 Just curious...what do you folks use to calibrate your refractometers? don't use rodi. Use calibration fluid. If there is a linearity error, if it's right at 0 it could be way off at 1.026. We care about accuracy near 1.026 so that is what you want to use to calibrate. Once they are set they really shouldn't need to be recalibrated. It's actually not a good idea to recalibrate with old solution. If anything evaporates out of the solutions it's salinity changes so you will be recalibrating to the wrong point. Link to comment Share on other sites More sharing options...
L8 2 RISE September 11, 2012 Share September 11, 2012 +1 to Hypertech, always use calibration solution. RO/DI water really is not a good substitute. As to the OP's question, if it took that long for all the water to mix, you might want to look into what kind of circulation you have going on. How big is your sump? What return pump do you have on it? Link to comment Share on other sites More sharing options...
Djplus1 September 11, 2012 Author Share September 11, 2012 +1 to Hypertech, always use calibration solution. RO/DI water really is not a good substitute. As to the OP's question, if it took that long for all the water to mix, you might want to look into what kind of circulation you have going on. How big is your sump? What return pump do you have on it? It's an Eshopps 75 sump and the return is a Mag Drive 5. Is that not enough for a drilled 72g? I bought this as a package at my LFS. Link to comment Share on other sites More sharing options...
L8 2 RISE September 11, 2012 Share September 11, 2012 That should be fine as long as the mag 5 is pushing as much water as it should (ie not clogged up or anything). That would be about 400-450 gph I'm guessing? So it was probably just that like you said, you changed the salinity so much it took a while for everything to mix. Link to comment Share on other sites More sharing options...
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