Actually, measuring salt water mixes by weight is the more accurate, measuring by specific gravity is less so, because for sg readings it depends on what temperature the water is.
I understand now how your refractometer could have messed things up.
Your refractometer should say in it's viewing window what temperature it was calibrated to at the factory.
Can I ask what calibration fluid you used, also which article you read regarding the difference between distilled and R/O?

I could see weight being accurate, however I wouldn't weigh it, it would be more of a 6 cups of salt makes this much water etc etc ... except my drum isn't filled to the same spot everytime, and measuring would never be exact (at least in my circumstances). Even if I had a fill line on the tank ... I wouldn't know the exact volume and so on haha.

My question about weight though would be this. Considering if I test Bucket A of my salt after mixed to 1.026, from lot 996 and I get 450 Calcium and 11 dKh and then I test Bucket B of my salt from lot 997 and get 470 calcium and 13 dKh ... would weight truly be accurate. Would the added minerals not offset the amount of NaCl in the solution?

I use Instant Ocean, but I've also seen lots of threads where people test their mixed up saltwater from different buckets of all sorts of brands and have varied parameters.

As for the article ... All I remember is someone posted a link to it on ReefCentral. It was a .uk link though, if that helps narrow it down.

Sorry if I keep pushing on this, but your claim of your corals showing no stress, after a year of lowering salinity down to 1.017 surprises me. I'm wondering if you are getting accurate results even now. Corals need a certain balance of ions in order to process their life functions, so they would have had to take in extra fluid in order to compensate for the lower available ions in the water column.
You have a great looking tank and I would hate to see it suffer for a preventable reason.

The only calibration solutions I've seen are ones that you use for a probe, which you have to warm up to 25C, or ones that are stated to be 35ppt, that you can use on a refractometer.
Having a calibration fluid at 1.026 without stating at what temperature, leaves a critical bit of information out.

Other than a bit of faded purple on my bonsai ... I have no signs of stress on my tank. I just posted a recent full tank shot and everything seems to be doing great.

The solution I bought is a Pinpoint Marine solution from Reef Supplies. It says right on the bottle 1.026, 53.0 mS, and 35 ppt. Thats what I used to recalibrate the refractometer. And I had it at close to 25c because I keep the room warm as opposed to running multiple heaters in my little fishroom.

You may be right, the salinity may or may not be as low as it is. For all I know, the calibration solution isn't spot on ... tough to tell for sure. I have a hydrometer thats worth about $100 that floats. It's glass and bobs in the water and indicates your level. I don't use it because you have to kill all your flow and pumps to get an accurate reading, but perhaps I will break it out to try and see how far off the refratometer actually is.

I would guess that the 1.026 number is for 25C, but your refractometer is calibrated for 20C, which would mean the reading is still off.
Next time you use your refractometer, see if the scale in the viewing window has a 20C or 20/20 symbol. That would confirm it.

Some refractometer scales in the window have a conversion number right beside it. If yours does, see if it's in the ppt measurement.
If so, get your refractometer instrument to 20C and use that same calibration fluid, but calibrate to 35 ppt.

I agree, it looks great. I watch my corals to see if anything is wrong, then I use testing equipment to pinpoint what it is.
By the looks of your tank, very little, if anything is out of whack.
- so I hope you're not fixing a problem that doesn't exist.:smile:

Amen to that, me neither lol