persistently rising specific gravity

[kurtp]

My 125 gallon mature mixed reef tank has had steadily rising SG for a couple of years. If I don't siphon off a few gallons of tank water on a regular basis and let the ATO RO/DI water refill the loss, and/or do dilute water changes the tank water will just slowly keep climbing, and I can't figure out why. TDS of my RO/DI water is 0.0, and I have changed out the 6 chamber filters/media on my unit. The containers for the ATO supply have all been replaced (I thought maybe there had been some contamination over time) I have used BRS two part dosing for many years but don't add any other supplements. I run a skimmer and ATS and feed LRS or Rods reef food, all of which I have done for over a decade without any prior issues. I can't figure out why this is happening. Looking back it seems to me the issue started about the time the BRS 2 part was changed to 'Pharma' grade but after talking with the BRS staff I guess that is just a coincidence because no one else has reported the issue.
Any suggestions would be appreciated.
My parameters fluctuate slightly due to the dilutions I keep doing but range as follows: Alk :9.0 - 9.5 (Hanna), Ca: 380 - 450, Mg 1150 - 1300. SG has gotten as high as 1.0300 but now I can keep it down in the 1.0270 - 1.0290 range, depending on my diligence with the annoying water dilutions.
Thanks,
Kurt

 

[homer1475]

2 part will raise salinity over time. Calcium chloride(chloride is salt) in particular.

Now that I go back and reread the OP..... I don't think 2 part will raise it that much? How much are you dosing?

 

[kurtp]

I have timers set for dosing pumps, I go through a gallon of calcium solution in about 4 days, and a gallon of the Alk solution in about 5 days. I add Mg on an as needed basis.

 

[biophilia]

@homer1475 is right on the money. If you are dosing quite a bit, that will cause the rise. You can try running your skimmer wetter if you want which will help to offset the salinity rise.

Another thing you could do if it's getting really annoying is to offset some of your 2-part dosing by setting up another dosing pump head with a reservoir of fully-saturated kalkwasser solution. Kaklwasser won't add sodium chloride to the system like 2-part, so a combination of kalkwasser supplemented by 2-part will add a lot less sodium chloride overall.

Or just keep siphoning out some tank water to compensate, but be aware that the sodium chloride added by the 2-part is not adding any trace elements. You can balance that through periodic water changes or by dosing them manually.

Have you double checked your alk and calcium test kits and process? It seems like something is off with how much you're dosing...

 

[madweazl]

I have timers set for dosing pumps, I go through a gallon of calcium solution in about 4 days, and a gallon of the Alk solution in about 5 days. I add Mg on an as needed basis.

You're dosing 750+ml of alk and 940+ml of calcium per day in a 125g tank? You've mixed the 2 part per the instructions on the label (e.g. 2 1/3 cups per gallon of water and 2 1/2 cups per gallon)?

 

[kurtp]

@homer1475 is right on the money. If you are dosing quite a bit, that will cause the rise. You can try running your skimmer wetter if you want which will help to offset the salinity rise.

Another thing you could do if it's getting really annoying is to offset some of your 2-part dosing by setting up another dosing pump head with a reservoir of fully-saturated kalkwasser solution. Kaklwasser won't add sodium chloride to the system like 2-part, so a combination of kalkwasser supplemented by 2-part will add a lot less sodium chloride overall.

Or just keep siphoning out some tank water to compensate, but be aware that the sodium chloride added by the 2-part is not adding any trace elements. You can balance that through periodic water changes or by dosing them manually.

Have you double checked your alk and calcium test kits and process? It seems like something is off with how much you're dosing...

Thanks, I have started to do a wetter skim than I used to and it does help. I will start to learn about Kalkwasser, something I have never looked into.

 

[kurtp]

You're dosing 750+ml of alk and 940+ml of calcium per day in a 125g tank? You've mixed the 2 part per the instructions on the label (e.g. 2 1/3 cups per gallon of water and 2 1/2 cups per gallon)?

I know, it is a high volume, but I had attributed that to the maturity of the tank and how large the SPS corals had gotten--figured the gradually increasing consumption of alk and Ca was do to that. I tend to mix my Alk more concentrated with 2 1/2 cups per gallon simply because I have a half cup measuring cup that I keep out in the RODI, reef equipment shed. Maybe that is contributing to the issue? Pretty lame of me if it is, since I should be able to fit a 1/3 measuring cup into my reef budget.

 

[kurtp]

@homer1475 is right on the money. If you are dosing quite a bit, that will cause the rise. You can try running your skimmer wetter if you want which will help to offset the salinity rise.

Another thing you could do if it's getting really annoying is to offset some of your 2-part dosing by setting up another dosing pump head with a reservoir of fully-saturated kalkwasser solution. Kaklwasser won't add sodium chloride to the system like 2-part, so a combination of kalkwasser supplemented by 2-part will add a lot less sodium chloride overall.

Or just keep siphoning out some tank water to compensate, but be aware that the sodium chloride added by the 2-part is not adding any trace elements. You can balance that through periodic water changes or by dosing them manually.

Have you double checked your alk and calcium test kits and process? It seems like something is off with how much you're dosing...

I just read the instructional blurb about Kalkwasser on BRS site, it sure seems simple enough so I just ordered some. We'll see how that goes. Thanks

 

[Randy Holmes-Farley]

I just read the instructional blurb about Kalkwasser on BRS site, it sure seems simple enough so I just ordered some. We'll see how that goes. Thanks

I used it for 20 years. The main limitation is that you cannot dose more than the daily evaporation, and so it cannot keep up in many cases.