Brown residue in saltwater storage container

[andrew james]

I've noticed a brown residue on the insides of my saltwater storage container with a slightly gritty consistency. Anyone have any ideas?

A little about my system to use as clues.

Red Sea Blue bucket salt
RODI container has no such residue.
I use a Spectrapure MAXCAP 90 gpd filters are two months old with approx. 300gal through them.
TDS is 51 into the system after first two carbon filters it is 0 and 0 in and out of DI resin.
My saltwater container is heated to 75 f. and has a powerhead in it to keep it mixed.
I've tested the water and nothing seems out of the ordinary. I'm concerned it could be rust or something but that's probably overreaching. I just cleaned it out two weeks ago so this build up is pretty quick. Any help would be awesome.

 

[stunreefer Verified Sponsor]

Generally this is caused by an anti-caking agent. Some salts do not use them, some do.

If the salt is not continuously turned over calcium can precipitate out and leave a similar residue. Always best to check storage recommendation from the manufacturer, as not all salts are the same.

 

[spinycheek]

I've always had that too, I try to just let it settle so it's not going into the tank, then rinse it out when the storage container empties. I've never noticed it affecting the aquarium.

 

[nemo1017]

I believe heating the salt while mixing causes precipitation. Don't heat it while mixing, heat it just before you're ready to use it for your water change.

 

[andrew james]

Thanks all I just switched back to Red Sea blue and it seems like that when this started.

 

[andrew james]

I heat the water but it's also being constantly mixed. My basement is unheated and the water would end up being in the 30's all winter if I didnt. I haven't noticed precipitation at least not the usually variety.

 

[gcarroll]

I always scrubbed the sides of my mixing container while pumping in the water. It always cleared up within minutes. I never found it harmful and corals seemed happy. I figuered it was just organics since the salt was derived from NSW.

 

[nemo1017]

Most Calcium based salts precipitate out in warmer water vs room temp or colder water. More than likely it's calcium carbonate build up....kinda like how pumps and heaters collect buildup faster then anything else in your tank.