Rock/vinegar test: Can I use apple cider vinegar?

[largo]

River rocks are a solid choice. I've used them in my tanks for years without issues. Just give 'em a good scrub and vinegar test, and you should be golden.

[Cody]

Agreed on the river rocks. They're usually safe, but testing is smart. My Oscars are picky, so I always double check everything before it goes in the tank.