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Alkalinity seems off in fresh saltwater mix

Klatzy

Supporting Member
My alkalinity was a bit low recently (7-7.5 dKH range) when it's been in the 9-10 range in the previous months. I tested some fresh saltwater (mixed a couple days ago) and the Alk was measuring ~6.0 dKH (Instant Ocean Reef crystals). Reports online and my experience has this salt mix giving me around 9-11 dKH after a water change. I'm going to go get another Alk tester (I'm using a Hannah tester) just to double-check whether my tester is out of wack .

Would you recommend buying another bunch of salt mix and testing that in case my current batch is abnormal (assuming the new tester confirms the low Alk)?
 

Da_Neefer

Supporting Member
My alkalinity was a bit low recently (7-7.5 dKH range) when it's been in the 9-10 range in the previous months. I tested some fresh saltwater (mixed a couple days ago) and the Alk was measuring ~6.0 dKH (Instant Ocean Reef crystals). Reports online and my experience has this salt mix giving me around 9-11 dKH after a water change. I'm going to go get another Alk tester (I'm using a Hannah tester) just to double-check whether my tester is out of wack .

Would you recommend buying another bunch of salt mix and testing that in case my current batch is abnormal (assuming the new tester confirms the low Alk)?
Calibrate your refractometer if you can and haven't already done so. Low salinity will result in low Alk.

Mixed salt that sits for awhile can drop in Alk and Cal as well.
 

rdriggett

Supporting Member
So it looks like the Hannah alkalinity reagent is off (the API strip was reporting ~8.3 dKH). And the refractometer has drifted a bit, down to 1.020 when showing 1.026 specific gravity.
So that's at least 3 of us who have had inaccurate salinity cause whack parameter readings recently. @H2OPlayar, you, and myself. PSA to all!
 

rdriggett

Supporting Member
I always consistently mixed a fixed volume of salt mix with a fixed volume of water, and got consistent results that way. It sounds like you guys are mixing arbitrary amounts of salt and water until your refractometer gives you the number you want? Am I reading this correctly?
Yea...
 

Klatzy

Supporting Member
I calibrated each time for a while, then once a week, and now once a month. It was due for a calibration... I kinda do a rough calculation, I know that ~20 gallons + 3 large scoops was giving me about the approximate salinity. I could measure the salt out by weight and water by volume more precisely....I guess...
It does make sense though, with how much time and money has been invested, to ensure that I'm not causing dramatic salinity swings.
 
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Prestondeeply

Supporting Member
I always check the current tank salinity to make sure it matches the incoming SW...right before I do the water change. If the device is compromised, at least it will match. But it would seem like checking it that way and also driving 1.026 act as a double check.

But, with ato or dosing, drift could drive both out of range. So, I'm going to adjust to the fixed measurement and calibrate monthly model to see if I can avoid drift. What other ways are there? Multiple measurement devices?
 

Da_Neefer

Supporting Member
I usually calibrate every time i use my refractometer now after having a salinity issue myself. How often ya'll think it's worth replacing the refractometer? 2 yrs? 4?
 

Arvin R

Supporting Member
I weigh my salt when mixing. For my red sea coral pro 720g for every 5 gal of water. Dead on everytime at 1.025. I don't even check it anymore even though I know I should just in case. I will check my tank 30min after the water change and make any adjustments if needed but never had to so far.
 

JVU

President
BOD
I have a 1 gallon plastic pitcher that I have a mark on the side for the settled salt level that will give me the desired 35 ppt when added to RODI water the brute mixing container I use filled to the float level. It’s a little effort to set it up but then it makes it super easy and reliable going forward. Every time I check it, it is exactly 35 ppt.

Also if you are going to use a bargain salt like IO that is known to sometimes vary batch to batch then be prepared to have to check parameters of new water more frequently and sometimes be supplementing.
 

Prestondeeply

Supporting Member
At 78 temp and after a 12 hour mix, 5.7oz of IORC/1 gallon of RODI-0 worked for me.

I'm going to mark the bucket fill height and get a marked jug as @JVU said based on these measurements. I'll do it again this weekend to see if those measurements line up on a second repeat.
 

Klatzy

Supporting Member
So I measured out ~7 gallons (essentially 2 5gal home depot buckets filled to the 3.5 gallon mark) and 1680 grams of Instant Ocean Reef crystals mix (two large bowls worth, I may go to a more accurate measuring device) = 1.030 specific gravity. Added 1 gallon of water got me to 1.026. Mixed at 11 am, sat for about 2 hours (~76°F). Used a long handled mixer to stir it a few times. Calibrated the refractometer (did need adjustment), I think I'll calibrate it each time I make up significant amounts.
Also the low ALK readings were due to bad reagent, new reagent gave me 11.0 dKH, which is more line with previous readings, the bad reagent gave me 7.0 dKH.
 
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