Black discoloration on Alk dosing container

[CindyKz]

Over time I've noticed these black discoloration lines in my alk dosing container. They look almost like mildew, but that seems like an odd thing to have in alk solution. The discoloration is definitely on the inside. I noticed one or two black "floaties" in my alk solution yesterday so I pitched the remaining and rinsed the container. Rinsing didn't have any effect.

This has been going on for a while so I'm not so worried about harm to my tank, but curious what it could be and if I should retire the container.

 

[Hitman]

Never seen this before. What additive brand are you using?

 

[CindyKz]

Seachem Reef Fusion 1 & 2. There isn't any discoloration in the calcium container ;Bored

 

[Randy Holmes-Farley Verified Community Expert]

Probably metal oxides precipitating, like iron. I’d ignore it.

 

[CindyKz]

Probably metal oxides precipitating, like iron. I’d ignore it.

Thank you Randy! I'll do that. Happy Reefing!