Low Sodium due to HCl from Alk monitor?

[Drneil]

I've now had a second ICP returned indicating low sodium and hence low PSU, latest 29.30PSU!

Last ICP was 30.70, which ended up scrabbling with multiple refractometers and calibration fuilds making me happy my tank was at 35ppt.

Mg and K are at the low end, but Ca is normal. These are were I expect them to be compared to the last ICP at 34.74PSU.

No ill health from the corals but plan plenty of water chances to see if it corrects the issue.

Question is dosing HCl by returning waste water from the Alk monitor causing this issue? I'm no chemist so appreciate any words of wisdom.

Thanks

 

[Randy Holmes-Farley]

No, that addition will not reduce salinity unless you removed an equal amount of salt water. It's like adding a tiny bit of top off water.

Even if you did remove an equal amount of salt water each time, you'd need to have added and removed more than 12% of the tank volume, and thus used 12 gallons of acid in a tank with 100 gallons water volume.

 

[HuduVudu]

@Drneil so the saying goes nothing in this life is free.

Two part dosing has downsides and people either don't know or ignore them. Every way of maintaining Ca(Mg) and Alk is like this. If you are using a system you need to understand it's downsides, so you can properly compensate. Don't go outside the recommended way of doing something unless you very clearly understand the underlying principles.

The downside of 2 part dosing is that you are adding Na and Cl. There are two major effects of this. First it is important that Ca and Alk are dosed in proportion. Second, it is important that you deal with the Na and Cl getting out of balance with the rest of the elements. You can use Balling for the second part. The first part is tough because unless you are hand dosing, dosing pumps will tend to lean one way or another. The biggest issue is that other than ICP you can not test for Na and Cl in your tank.

The fastest way to deal with the entirety of balance is to water change. Just be aware of why you are water changing and what it is happening chemically speaking.

 

[Randy Holmes-Farley]

But his low salinity is not an effect of two part dosing, regardless of whether it is a complete mix or not. Low sodium also is not ever caused by two part dosing.

 

[HuduVudu]

But his low salinity is not an effect of two part dosing, regardless of whether it is a complete mix or not. Low sodium also is not ever caused by two part dosing.

Agreed the the low salinity has nothing to do with 2 part.

My issue is that Ca is "normal" and Na is "low". We don't have numbers so educated guesses are in order. If the salinity is brought in line then the Ca will be "high" (higher) and the sodium depending on the level will come up but might still be in the low range. Hence the tank being out of balance. How far the biome will accomodate this out of balance situation is unknown, but you will have to agree with me at some point there will be problems.

This is an indication to me that only one part of the two part is being dosed ... CaCl.

 

[Drneil]

Thanks for your replies, I dose all for reef and have done for almost three years. It was the carbo calcium DIY afr mix but now the AFR powder. So I don't expect any imbalance from this method.

The strange thing is I've done three ICP's this year, this huge drop happened between the first and second ICPs. Will summarise the main parameters below.

Jan 26th, 34.74PSU, Ca 425, K 365, Mg 1230, Na 11175, S 805
Feb 23rd, 30.68PSU, Ca 430, K 377, Mg 1258, Na 9466, S 813
April 28th 29.30PSU, Ca 438, K 361, Mg 1207, Na 8999, S 783

Between the 1st and 2nd other than all for reef only the addition is bio-magnesium to lift Mg. No water changes. Did multiple checks to confirm salinity was ok. Reported issue with ICP supplier.

My local reef shop chased the supplier and they offered me free test as they no longer had my sample. On the 3rd test I've done x3 20% water changes over the two months.

No issues with the tank and everything seems happy.

Fully understand your answer Randy, 0.02M Hcl is almost all RO, probably 2 litres max over the one month of that huge drop.

Going to get another ICP that reports chloride, but if I can put my finger on it I'll just increase the water changes.

Thanks