Slow Progress?

[W1ngz]

The cause to this could be the calibration method. I think in brewing, you calibrate to 0?
At 35ppt, the calibration can be skewed. I normally calibrate to my target with 35ppt calibration solution.

 

[Theaviator]

Which doesn’t make sense at all. I just calibrated the refractometer with distilled water. Thing may be broken is my guess. I have no idea. Guess I’ll just use a hydrometer from now on.
going forward. How does this effect my tank?

I just read your response. You Are correct. We calibrate to zero when brewing. My mind is blown right now.

 

[Theaviator]

Now the question I have. How quickly can I change this salinity? I was thinking just about 5 gallons a week of just fresh RODI water. No salt. Then test the salinity afterwards in the tank till it’s on track. Does this sound like a good plan so I don’t kill what’s left in the tank?

 

[W1ngz]

If you're using a decent glass hydrometer and cylinder, cleaned properly and often, then you could probably calibrate your refractometer based on that. You'll at least be on the green instead of in the trees until you get some proper reference solution.

You shouldn't change anything quickly in a tank unless it's something that is threatening imminent death, like an ammonia spike. What you could do, if you're using an ATO, is remove 2 gallons from the tank and just let the ATO slowly fill it up. If not you'll just have to add a few cups at a time manually over about 30 minutes. Do this each day for about 10 days until you get back to a normal level. Try not to change things more than 2ppt per day.

This calculator will help explain how I got those numbers.

 

[Theaviator]

Great. Again thank you! You figured it out. I owe you a home brew!

 

[TheKyle]

Calibration fluid should be better than distilled water since 0ppt is so far away from the value you are actually looking to test at. Something like this is recommended for calibrating even though the directions on the reftractometer say distilled water.

 

[TheKyle]

I think temperature plays a big role in refractive index also so if your calibration fluid or distilled water is really cold it can mess up readings. Some people recommend floating calibration fluid in the tank to equalize temp before.

 

[Theaviator]

Interesting, at this point I’m willing to try anything. I’m buying some now. I’m excited to get this finally figured out. And I’m thankful I still have an alive fish in there, somehow.

 

[W1ngz]

That's the bottle I use. Just keep in mind, that it does expire. As you use it, just a little water evaporates each time, and the accuracy will drift. I dump mine each year. Just take a sharpie and write a replace by date on it.

Most decent refractometers are temperature compensating. If everything is left at room temperatures, the real difference in SG for the few degrees difference between room and tank temperatures would be down in the 4th decimal place, below the margin of error for a hobby device. Leave the water on the lens for 10-20 seconds and it's fine.

If it's not temp compensating, that's a whole other thing and can throw you off by quite a bit.