Please Help Me Understand What's Going On With Calcium and Mg

[Scott07]

Thank you for the reply Randy. I've done some more reading, as well as re-reading your article about refractometers and calibration a few more times. I believe that I do understand what you're saying. And I also now believe it's far more likely that my refractometer was correct using the solution than it is now calibrated w/ RO/DI (wish I hadn't already brought my tank down .001 lol)

Ok, here are my next steps... let me know if you see anything wrong or that I'm missing:

-re-calibrate my refractometer using my solution standard
-take it to my LFS and compare against their refractometer
-unsure if it's better to compare readings between our two instruments, or if it would be better for me to have them check my calibration solution.
-stop worrying about why my calcium and magnesium are high.. just let it be before I do more damage than good lol. All things considered, my tank is doing pretty well, and once I figure out the correct salinity, I think i'm ready to leave well enough alone for a little bit.

Thanks for all of your help... Randy, bertoni, and anyone else who has commented. I would have crashed my tank out of ignorance long ago if it wasn't for this site and all the help I've recieved here.

 

[bertoni]

Using both refractometers to check the same saltwater sample should be good enough, whether it's the standard or a tank. I'm glad you're stopping the worrying part.

 

[Randy Holmes-Farley]

You can make a DIY calibration solution, and if you can measure accurately it will be as good as a commercial standard. If you use the tablespoons and coke bottles, it will be a rough check on the standard.

Reef Aquarium Salinity: Homemade Calibration Standards
http://reefkeeping.com/issues/2004-06/rhf/index.htm

 

[Scott07]

You can make a DIY calibration solution, and if you can measure accurately it will be as good as a commercial standard. If you use the tablespoons and coke bottles, it will be a rough check on the standard.

Reef Aquarium Salinity: Homemade Calibration Standards
http://reefkeeping.com/issues/2004-06/rhf/index.htm

I did actually see this earlier while researching, it's a cool idea ,I may give it a shot next time I'm feeling like a project. So... I took my refractometer to the LFS... and I love them dearly... but they calibrate theirs w/ RO/DI, so of course it matched mine exactly. They have some intelligent hobbyists there who say this is how they've always done it since the beginning of time, and it seems to have worked out for them lol.

So, thoughts from here. I think I'm just going to leave it calibrated to RO/DI for now... it matches both my swing arm and floating hydrometers, and the LFS's refractometer... and shoot for 1.025 to 1.026 with my WC water. I'm figuring even if it really is off .002, the worst I'm doing is keeping my reef at 1.023 which isn't anything catastrophic.

Makes sense?

 

[Randy Holmes-Farley]

Sounds fine. One reason it works for almost everyone is that our creatures seem pretty forgiving of the actual salinity.

 

[Scott07]

Sounds fine. One reason it works for almost everyone is that our creatures seem pretty forgiving of the actual salinity.

Yep, I believe you are correct. Life is really quite amazing in that it always finds a way.. isnt' it? I did try explaining that most refractometers are re-purposed brine instruments which is a different and less complex fluid that natural or artificial seawater.... and that the graphs of the refractive indexes of both fluids don't match at the salinity levels we aim for... but I think without reading your exceptional article on refractometer calibration, this is lost on most hobbyists.

Thank you for all of your help Randy and everyone else who has commented. I'm sure that I will revisit this issue of true calibration at some point in the future... but for the moment, I'm ready to leave well enough alone. Corals are either doing great, or on their way there (still think it was the phosguard)... and fish and inverts are happy as well, so I will take this as positive and try to just enjoy the tank for a while.

Next obstacle.... vacation.... lol

 

[Scott07]

Fwiw......

Fwiw......

After pondering this over for a week or so.... I've decided to calibrate back to the 35ppt standard. After researching and reviewing this particular issue... there are just too many other folks who have reported or commented on the exact same things I have observed (not that I don't trust your info at face value Randy! ). It seems much more likely that i'm observing similar phenomenon to others when comparing RODI to the 35ppt standard when calibrating, than that my standard is suddenly off. That said... I'll probably order another brand of standard in the near future just for comparison... and shoot for 1.024 rather than .25 or .26 w/ WC water just to be on the safe side.

 

[Aquarist007]

Using both refractometers to check the same saltwater sample should be good enough, whether it's the standard or a tank. I'm glad you're stopping the worrying part.

I would try to keep your tank parameters within the acceptable ranges rather then try to target for a specific number. It is less frustrating and less worrying

 

[Randy Holmes-Farley]

. there are just too many other folks who have reported or commented on the exact same things I have observed (not that I don't trust your info at face value Randy! ).

Always good to have practical experience backing up the scientific expectations.