Backyard Aquaponics
A place to discuss aquaponics

I have noticed something interesting since i bought my salt refractometer i have been doing some experiments when you put 3 kg of salt in a 3000 litre system and given time to circulate it only reads 1.5 ppm and after circulating for 3 hrs it comes back to under .5 ppm

Could be wrong, but isn't 3kg in 3000lt = 1 part per thousand? Did you add it after dissolving in hot water or just chuck it in? It may have just sunk to the bottom if not dissolved. How much did u pay for ur salt thingy?

Ebay $22 and probley had .5 from before another edit should be 3 days not 3 hrs

its not a hydrometer... the thing you float in the water? Like when making beer?

No this

Been doing some reading FF, in Stickneys book, Aquaculture,An Introductory Text, published by CABI publishing, Oxfordshire, UK.

Salt is def ppt, parts per thousand, or per millilitre not per million. Hand held refractometers have an accuracy of plus or minus 1ppt. As you have only added 1ppt, 3kg in 3000lt, your reading could show as zero or 2ppt. The more salt u add, the closer u will get to a true reading.

If u are looking to treat fish, you need to add another 9-12 kgs, to get your total salt up to 4-5ppt.

If you were just playing around to check ur new toy, do it on a smaller scale. Add 5,10,15,20,25 grams to a litre of water, then test. You should find the measurement will be closer to spot on, the more salt u use, (as variation is only plus or minus 1ppt.) Hope this helps.

There is an excellent half page on how fish regulate salt in both fresh and salt water, in the same body of text i was reading. If people are interested i will type it out.

how does that gadget work FF

i have access to a TDS meter that can be set to test based on different salts incuding the sodium choride is the same thing as that ?

I believe it works by lifting the clear plastic cover, adding a drop of water to the scale/lens bit, and then lowering the cover. Then you look through the eye piece and will see a scale with the salinity marked on it. Assume it works by different salinities refracting different distances....

correct daniel

yes daniel

Done a few experiments with a small 50 litre aquariam today that meter is spot on

Can you give us a run down of what you tested, how you did it and the results F&F?

Hi yes today started with 50 litre of fresh water 0 added 5 lots of 5 grams meter went up in 5 equal jumps to 5 ppt thats providing i am reading the scale right

your 22 bucks is looking like a bargain.