Are lava rocks aquarium safe or dangerous for fish?

Lava rocks can be used safely in fish tanks. Due to their porous nature they add to the beauty of the aquarium. They allow heaps of beneficial bacteria (BB) to grow on the surface & inside holes that will make sure that aquarium water remains clear.

Good bacteria that spread on the lava rocks are responsible for removing every ammonia byproduct from the water & keeps water clear.

Lava rocks can be used as substrates because they are relatively cheaper than other substrates. It is possible to mount plants to lava rocks. Lava rocks are best for carpeting plants & plants can easily attach their roots to porous lava rock.

Lava rocks can be used to offer a natural look to your aquarium. Fish like natural habitat inside aquariums so adding lava rocks can help make caves or structures, where stressed fish can hide, fries can hide from the bullies, & fish use caves as shelters. Some fish lay their eggs inside caves.

Are lava rocks aquarium safe or toxic for fish?

Lava rocks can be used in filters for biological filtration:

Lava rocks are very porous which make them the best choice for good bacteria to grow inside the holes. Beneficial bacteria are used for providing the ideal environment for the fish as they can transform highly dangerous ammonia into relatively less dangerous nitrites, & further transform it into even less dangerous nitrates. Good bacteria will be growing in the aquarium after the nitrogen cycle completes. Heaps of beneficial bacteria grow on the surface of bio media inside the aquarium filter.

Ordinary bio media can’t remove nitrates from the water but lava rocks are cheaper & can perform double duty. Lava rocks can clean every impurity because they offer both nitrifying & denitrifying bacteria which means they can remove ammonia, nitrites & nitrates from the aquarium water.

Water can enter the inside of lava rocks through tiny little pores, then the inside bacteria will absorb oxygen & will offer an oxygen free environment inside the rock.

Denitrifying bacteria grows in oxygen free places where they can absorb nitrates.