The easiest way to use a refractometer?

[Walkerrobin]

I have now got my refractometer, it is second hand and only been used once. There seems to be a lot of discussion on the net about the best way to calibrate it as some articles mention that the instructions are not great for tanks. What is the easiest and best way to get the refractometer calibrated and what readings should I look for? Im sure there are other novices out there that would like to know!

Thanks!

 

[Fishguy2727]

The only way I have ever heard to calibrate them, and the instructions on every one I have ever used including at the animal hospital, is to use distilled or pure RO water and adjust it if needed to read 0. If you do this the readings you get with saltwater should be very accurate.

 

[iDream]

What about the calibration fluids? It's supposed to be like sea water I believe.

I just don't want to waste my money on the stuff if it's not necessary

 

[The bods]

I have a D&D refractometer,I use RO (pure)to zero it,although that they are very accurate you must remember to calibrate every time you use it,this can be the tricky part!so unless I think I need to find exactly the salinity in my tank I just use my trusty hydrometer 

 

[joy13]

My refractometer is always dead on I have never had to recalibrate it. Mine has a screw and not a thumb screw to recalibrate, I believe this may make a difference. There is a saltwater store near me that will double check mine against theirs if I feel the need.

 

[The bods]

I would still say it's best to re-calibrate it after every 2weekly water changes,but asking your local fish store to check it against there's is always a good idea

 

[Walkerrobin]

Thanks all - As there is such a small amount of distilled water to be placed on the Refractometer will condensed steam suffice from the Kettle? and what readings should i look for when i take the true test?

 

[The bods]

I'm not so keen on using the steam idea however I think it would work,I have 3 tanks set up 2 freshwater and my saltwater so for me I've always got RO laying around,when you do water changes what are you putting back in?once calibrated in RO the refractometer will read 0

 

[Walkerrobin]

Thanks - my water is pre-mixed from the LFS....i bought the Refrac to make sure everything is safe when i do / and after my PWC.

 

[joy13]

If you buy your water from a LFS make sure you test it every time before you use it. You could check the water now to see what it is at so you have a base line to go by.

 

[Kurt_Nelson]

If you want your refractometer to read accurate at 1.000 then use pure water. If you want it to read accurate at 1.026 then I'd suggest using calibration fluid.

Without getting all technical, using a single point (either pure water or calibration fluid) to calibrate is only useful for a small range around that single point. To be accurate over a range of readings, you would need a two-point calibration, but the hobby grade refractometers we use don't have that option.

Some refractometers may end up being accurate over the entire range (1.000 to 1.026) and some might not. It all depends. Mine isn't, and is off by about 0.002 depending on what I use to calibrate it with. I know other folks with refractometers that measure perfect over the entire range. But you'll never know what one you have until you get some calibration fluid and try it out!

 

[Fishguy2727]

You should be using RO for topoff even if you but water change water premixed.

 

[Walkerrobin]

Thanks. Fishguy - can you explain what you mean. I think I know?!!

 

[Fishguy2727]

Do not use saltwater to top off the tank. When you have evaporation only water leaves, not salt. If you top off with saltwater your salinity will go up over time (I have a client who did this and found out it was 1.045 when he finally bought a refractometer). Use saltwater for water changes and RO for topping off.

 

[Walkerrobin]

You are going to have to ignore my ignorance, Topping off is adding RO when salt water is evaporated? Thanks

 

[austinsdad]

Correct

 

[Walkerrobin]

Cheers, could this evaporation effect ph levels if you don't top off with distilled water, and do you just add a fraction of it at a time?

 

[Fishguy2727]

The more often the better, at least once a day. If you can top off at least two or three times that is even better (in the morning, when you get home, before you go to bed). The more frequently you top off the more stable the salinity. It also means that when life happens and you miss a top off it is much less likely to become a serious issue.

 

[Walkerrobin]

Great thanks