Mystery snail question

[SadSoyBeans]

So whenever i put snails in my 5.5g they die within a day or 2, but whenever i put them in my 10g they thrive. They have very similar water parameters and are both fully cycled, the tanks are basicly the same except for the decorations, fish stocking, and gravel depth. I always stir around my substrate to prevent anaerobic regions. Do any of you have any ideas why this happens?

 

[TMaier]

Detail to differences. A single rock with traces of copper could make all the difference.

 

[SadSoyBeans]

I feel like that might be the most plausible answer, my substrate might have a bit of copper, but in the larger tank it gets diluted a bit more. That might be it, but idk for sure.

 

[kashif314]

Detail to differences. A single rock with traces of copper could make all the difference.

Really very very best possible answer. Applause