Question about seashells/calcium carbonate/PH balancing

[Ula Hula]

I use eggshells in my tank as a source of calcium carbonate to buffer the water, but I also have seashells in there and I'm wondering if they also do the job since they consist mainly of calcium carbonate. In the tank set up section of this website I see that Mustafa mentions limestone and coral as usable substances for c.c., but I'm wondering if there's a reason why seashells aren't mentioned. Thanks!

[Mustafa]

Sea shells work fine, but one of the reasons I did not specifically mention them is because you need to hand-collect them. If you buy decorative sea shells online, they are usually coated with some kind of chemical to make them shiny (even if the seller says they are not), which has been the cause of shrimp deaths in the past.

[Ula Hula]

Okay, thank you for clarifying that!

[senideldino]

The seashells from shop indeed leave a white trail, lucky no death in my tank.
Before covid i used to collect tiny colorful shells for my tanks.

[Mustafa]

Okay, thank you for clarifying that!

No problem!