Which stone is best for a fish tank?

The best stone for a fish tank is commercially prepared aquarium stone that has been cleaned and tested for mineral content and contaminants. For a freshwater tank, choose a non-calciferous, inert stone that won't change the pH and mineral composition of your water—good choices include quartz, granite, and slate. For a saltwater tank or fish that need hard water, you may want to choose coral or limestone gravel that adjusts the chemistry of your water.

Is it necessary to put stones in aquariums?

It isn't necessary to put stones in aquariums—you could choose another substrate like sand instead. Both allow beneficial bacteria to flourish, which provides important biological filtration for your water. However, many people prefer the look of stone and enjoy the convenience of using a gravel vacuum to clean.

Should I boil rocks before putting them in an aquarium?

You should not boil rocks before putting them in an aquarium, as there is a risk of the rocks exploding. Some rocks contain air pockets that can cause bursting under high heat. If you choose a commercially prepared stone made specifically for use in fish tanks, you should not need to worry about boiling to sterilize them.