Refractometer calibration? 0ppt vs 35ppt

[rojees]

So I recently bought a handheld Refractometer, the seller at the LFS calibrated it for me.

I'm a newbie and it didn't occur to me ask how he calibrated it. Now I'm at home and I want to know how its done properly as I will start my tank cycle soon.

The manual that came with Refractometer says calibrate it to 0, however, from youtube and general googling, a lot of people calibrate it to 35 ppt.

Which one should I go for?

 

[Lukeluke]

35. You want to calibrate it to as close to what you want your salinity to be as possible. Reduces the error. For example, mine is calibrated to 35, but reads ro/di water at less than zero.

 

[The_Skrimp]

Use a 35ppt calibration fluid for the most accurate calibration. If you’re in a pinch and don’t have any fluid, calibrating to zero using just RO water is usually fine.

 

[Aquachristik]

The 35 ppt liquid is pretty cheap and will last you a good while. I've had my current calibration liquid for over a year and its just a little below half way.

 

[Trouble1375]

I keep 2 bottles of calibration fluid - 2 different brands and calibrate every Sunday when I test. They are both supposed to be 35ppt but they test slightly different so I test with both and then adjust to the mid-point.

 

[Jeffcb]

Calibrate it every time you use it btw.

 

[vetteguy53081]

My solutions (2 types) both suggest 35ppt

 

[PatW]

I recommend the 35 PPT calibration. You really probably do not care if you can measure 0 PPT accurately. You care about your accuracy at or near 35 PPT.

 

[Garf]

You can make a DIY calibration solution for pennies, just with RODI and table salt.

 

[rojees]

Thanks for the replies guys.

I finally figured out the tiny solution the lfs seller gave me was distilled water so he calibrated it to 1.0000.

I’m assuming you all are advising me to calibrate to 35ppt is based on using calibration solution, which I don’t have but will look to get some!