Trust LFS or Your equiptment?

[BrandonFlorida]

So I took my water up to the LFS so I could have them double check my test and also because I do not have a phos test kit.. They checked salinity and it was at 1.023 but he used RO water to adjust the refractometer to zero. I bought some calibration fluid to set both of my refractometers and my test shows it as 1.025. Could I have a bad refractometer and has anyone ever had this happen to them?


My mag is low like 1200 and calcium is lowish at 400. I am upping the mag first and then will adjust calcium once mag is around 1350.

Alk 9
PH 8.2
Phos 0
Nitrate 0
never tested ammonia
sal. per my test 1.025 (1.023 from LFS using RO water)

Is there any better way to get mag up? I am using seachem mag to up it but it doenst go far and its expensive that way.

Edit: Tank is 180 gallons with Chinese leds and jeabo rw15s

 

[MondoBongo]

if you calibrated your refractometer using a reference solution, i would believe yours. calibrating to 0 is not helpful when you're looking for a higher range, that's pretty much true of any instrumentation. you want it calibrated to the range you're looking for.

as far as the mag, maybe the BRS additives?

http://www.bulkreefsupply.com/calcium-alkalinity-trace-elements.html

you would need magnesium sulfate and magnesium chloride to mix up the solution:

http://www.bulkreefsupply.com/instructions/article/Instructions-for-Bulk-Packaged-Materials

i switched to their two part dosing recently, and with the 1/2 gallon containers of mag, i've mixed up enough mag solution to last me a loooooooooong time.

 

[Bent]

Using RO water to calibrate a refract will be inaccurate.

 

[snorvich]

if you calibrated your refractometer using a reference solution, i would believe yours. calibrating to 0 is not helpful when you're looking for a higher range, that's pretty much true of any instrumentation. you want it calibrated to the range you're looking for.

I agree. I am surprised the LFS did that.

 

[BrandonFlorida]

I agree. I am surprised the LFS did that.

I even said something to the kid doing it, and he just shrugged his shoulders.. I used to do it that way as well until I was informed about using calibration fluid.

So I will trust my test vs. theirs. all other test were exactly what I had.

if you calibrated your refractometer using a reference solution, i would believe yours. calibrating to 0 is not helpful when you're looking for a higher range, that's pretty much true of any instrumentation. you want it calibrated to the range you're looking for.

as far as the mag, maybe the BRS additives?

http://www.bulkreefsupply.com/calcium-alkalinity-trace-elements.html

you would need magnesium sulfate and magnesium chloride to mix up the solution:

http://www.bulkreefsupply.com/instructions/article/Instructions-for-Bulk-Packaged-Materials

i switched to their two part dosing recently, and with the 1/2 gallon containers of mag, i've mixed up enough mag solution to last me a loooooooooong time.

Also thanks for the mag info, I will be using it once I deplete my mag which should be very long..

 

[stonecold]

Every 3 months, I use this to calibrate my refractometer....

I trust my equipment(s).

 

[snorvich]

Every 3 months, I use this to calibrate my refractometer....

I trust my equipment(s).

You should periodically reorder or make sure no evaporation can occur.

 

[BrandonFlorida]

Every 3 months, I use this to calibrate my refractometer....

I trust my equipment(s).

Yep that's what I use now. I just feel bad for all the other customers who are trusting their refractometer..

 

[FarmerTy]

I trust my own equipment. At least where I'm at, I have better test equipment than the LFS here.

 

[heathlindner25]

I use calibration fluid ,but some refractometers sold at local fish stores....in the instructions say to calibrate with ro/di water

 

[BrandonFlorida]

I use calibration fluid ,but some refractometers sold at local fish stores....in the instructions say to calibrate with ro/di water

My last tank and refractometer was done with rodi water and It was on point but I figure that calibration fluid would be best being your setting it to the 1.026 that you are testing for.

So when you set rodi water at zero being no salt is in the water, how come it doenst work correctly? Is it because your not testing for zero but testing for the correct salinity? Just curious..

 

[MondoBongo]

you're effectively looking for a set point, and when you have a known quantity such as a reference sample that matches the precise value you're looking, it will be more accurate than doing just a single low calibration.

that way, it minimizes the risk of the instrument being off relative to itself.

for example, let's say you calibrate your floor with RODI, your 0 is now perfect. but you're not measuring for 0, you're measuring for 35ppt. so if your refractometer is off by a few percent as it goes higher up the scale, suddenly you have an invalid result in your high range.

just to be clear, i would consider a refractometer calibrated with RODI water better than one that wasn't calibrated at all, but for the best results i would use a 35ppt calibration solution.

if you're off by a few ppt it's not the end of the world. i've seen it said that it's more important to be stable than to be perfect accurate, and within a reasonable amount of variance, i agree with that.

 

[BrandonFlorida]

Ok I see. Makes sense that you would want it set to where your testing at.. Thanks Mondo