Adding Stones To Aquarium

[Walkerlr]

Hi, I was wondering if it is safe to add these rocks I found on the beach into my freshwater aquarium. They are tan and smooth. I know that certain rocks are a no no for lower ph aquarium, but I'm not sure what kind these are. I tried attaching a photo several times, but the site said I was not allowed to?
 
Also, are seashells safe to add? I want to be absolutely sure.
 
 

 

[Munroco]

wash the stones well and they will be fine, you can test if stones are suitable by pouring a little vinegar on them, if it fizzes then best not to use them. shells are a different matter, they will leech calcium into the water. This is fine for some fish but not so good for others

 

[Walkerlr]

Thanks! I'll try out the stones