These beautiful, one of a kind Conglomerates are the perfect choice for any aquarium and any type fish as they are inert and won't change the parameters of water. Conglomerates form when a group of rocks roll and travel in a waterway for long periods of time. During that time, very fine pieces caught in between, grind down into a cement type substance that bonds all of the rolling rocks into one solid piece. The type of rock that make up the Conglomerate determines what kind of fish and fish tank they're compatible with. These have a mix of chert and chalcedony which make them completely safe for all fish in any aquatic environment.
If you zoom in on the photos you can see the detail of the many rocks that cemented together to create each unique piece. These pieces are permanently bonded by nature and will remain in tact just like they are now. The only way these rocks would come apart is if you dropped one on hard surface or hit it with a hammer with the intention of braking it.
The distinctly different surfaces of these two look good next to each other as they give good contrast while the cave and holes provide features your fish appreciate. 

The big one on the left measure 13" x 12" x 7".  3/4 of the inside is hollow, making a cave big enough for your large fish. The other big rock measures 12" x 12". It is covered with small and medium sized holes your smaller fish and fry need when they're looking for protection. 

Everything you see pictured have a total weight of 50 lb. and everything pictured is included.  Free Shipping and Free Returns