Will heat affect humidity contaminated salt mix?

Skydvr · Mar 19, 2017

I live in a basement apartment and tend to have moisture issues. With pico tanks, I tend to not go through salt mix very rapidly and no matter what I do, I seem to end up with moisture contaminated salt before I make it half way through (usually the end of summer). Sealed bags in sealed buckets with multiple large silica packets don't seem to help in late summer. I'm about ready to switch over to ESV just to not have this issue anymore.

This last batch was mixing up fine despite the moisture in the mix. I would just have to add a little extra salt due to the increased volume, but the calcium was around 420 and magnesium was around 1300 and it was mixing clear (35ppt). A little lower than normal, but still acceptable.

For what ever reason I decided to try to dry the mix out by placing it in front of the heater. Now when I mix up some water, there is precipitate and parameters are lower, Mg <1000 and Ca <350 and I need to run the water through a fine sock to clear the water a bit before adding to the aquarium (as well as dosing to bring Mg, Ca, and alkalinity up). I left the bag there and it has gotten worse. I have not tested yet, but the bucket, pump, and heater are covered in precipitate.

My question is, does heat effect the formation of calcium carbonate in the damp salt mix or was there some anomaly that caused the top layers to be okay while the lower layers bound the calcium and magnesium? Do you think mixing the salt for a bit before plugging in the heater will make a difference?

Randy Holmes-Farley · Mar 20, 2017

Yes, I expect you drove the precipitation of calcium carbonate.

What was your concern with it being moist?

That said, if the alk is OK when the water is clear and settled, salt mixes are OK to use.

Skydvr · Mar 20, 2017

I was thinking the moisture alone would cause the precipitation. I had slight reservations about the heat; I should have asked the question before putting the salt in front of the heater. I was seeing a slight shift in Ca and Mg, but levels were acceptable. I should have left well enough alone. I thought the moisture was going to keep causing the Ca and Mg to creep down. It looks like the heat accelerated that process.

It was a little bit of a pain hitting my desired SG since the volume increased with the moisture and it would take a bit more than half a cup of salt per gallon. It would take a couple extra additions of salt to bring SG up (and time for everything to mix and settle) and then adding RO to bring it back down. I only need to mix one or two gallons at a time, so the small variation in volume makes a significant difference.

Randy Holmes-Farley · Mar 20, 2017

Skydvr said:
I was thinking the moisture alone would cause the precipitation. I had slight reservations about the heat; I should have asked the question before putting the salt in front of the heater. I was seeing a slight shift in Ca and Mg, but levels were acceptable. I should have left well enough alone. I thought the moisture was going to keep causing the Ca and Mg to creep down. It looks like the heat accelerated that process.
.

The thing to monitor is alkalinity. Precipitating ALL of the alkalinity out of seawater would only drop calcium and magnesium together by roughly 50 ppm. So taking out half of the alkalinity would still leave most salt mixes as having adequate calcium and magnesium.

Skydvr · Mar 20, 2017

I really need to start learning chemistry. There is so much that I find interesting and engaging about it, but I was to burned out and just completely done with school by the time my schedule allowed for me to take a chemistry course.

Thanks for the info.