RO/DI problem ???

[sponge brain]

I purchased a Kent Marine Hi-S Maxima RO/DI 35gpd unit about 60 days ago. I set it up to fill through a Kent float switch mounted in a rubbermaid 30 gal new/clean trashcan. I also put a heater, a maxi=jet 900 powerhead and an airline with an airstone from an external airpump.
The first 45 days I was using Instant Ocean salt. Then about 15 days ago I switched to using Reef Crystals salt.
The PROBLEM?QUESTION = For the past week I have noticed a very light/thin grey/white dust like coating appearing in the rubbermaid container. It is covering the pump heater and airline. It wipes off very easy, yet , I notice the light residue is also left on the ******** bucket walls after carrying water to one of my tanks.
I have not been able to detect any noticeable residue in the aquariums after using this water for topoff and/or water changes.
Any input on what this dust film is and how to eliminate it ?

 

[broomer5]

I'm guessing that it's some calcium carbonate precipitating out of solution and settling on the solid structure of the plastic container.
Are you aerating the RO/DI before adding the salt when you mix a batch ?
Try mixing the salt powder slower, add some salt, mix it, let it sit a few minutes, add some more ... continue until the salinity is right.
It may be excessive CO2 gas in the RO/DI water - and it's not reached equalibrium with the atmosphere in the room yet.
When you add the salt - some of the calcium and carbonates combine and become a solid.
This can happen - especially if you're seeing it on the heater.
I've noticed this too before, when I used Reef Crystals vs Instant Ocean.

 

[sponge brain]

Thanks for the reply,
I had emailed Kent Marine with the same question and they emailed back exactly the same theory you did.
I was adding the salt quickly, so now I am doing so much slower.
By the way, which salt did you end up preferring ?

 

[broomer5]

Always used Instant Ocean in the past.
Tried a bucket of the Reef Crystals last year, but now I'm back to using IO.