What Kind Of Rocks Do You Not Put In A Fish Tank?

I would think any kind of rocks could be used in  tank. you can normally buy the pebbles at pet store to use, some stores sell river rocks or you can find your own , just make sure they are all washed off before adding them to the tank.

You can add any sort of rock as long as it's been washed and it's not sharp. Slow swimming fish which have a round circular body tend to get injured when sharp pointy objects are placed into the aquarium! Good luck