Precipitate in saltwater dosing line

[Joe Rice]

10 months ago I set up an auto water change system using the Neptune DOS. It's been working like a charm but I started to notice that a precipitate was forming inside the tubing that was delivering new saltwater (Instant Ocean regular) to the tank. Notably, there was no precipitate in the tubing that was pulling new saltwater from the reservoir to the DOS.

Today I noticed no new saltwater was being delivered to the tank. It turns out that the silicone tubing inside the DOS pump head was clogged with the same precipitate I've been seeing in the external tubing.

The precipitate doesn't dissolve in RO water (no surprise) but it did dissolve in a citric acid solution although it took a while and without a lot of bubbles forming.

So I'm wondering what this precipitate is and why it's forming?

Anyone else had this issue?

 

[MnFish1]

Curious - do you have your tubes entering the water 'under the water line' - if so that can cause this

 

[Joe Rice]

Curious - do you have your tubes entering the water 'under the water line' - if so that can cause this

Nope. There's a 6" air gap between the end of the tube and the water in the sump.

 

[Randy Holmes-Farley]

Many high alk salt mixes (including normal IO) have substantial precipitate. I’d suggest letting it fully settle before using it, and run acid through it occasionally.