Types of Fish Tank Rocks

There are a lot of different fish tank rocks or stones one can use in a tank. It is important when deciding on which to use that you make an informed decision when adding rocks to your tank.

fish tank rocks

Stones or Rocks?

It has become a very popular trend to use rocks or stones in a fish tank as you can purchase a lot of different shapes, sizes, and colors according to your liking at your local pet store. Just make sure that the rocks you add are not dangerous, especially if they are full of chemicals and other minerals that can kill your fish over time.

Something to keep in mind

  • Always make sure to avoid rocks with sharp edges and with small pores.  You may round off the edges of rocks with sandpaper.
  • Real stones will displace the water and weight of oxygenated water for your fish, thus artificial rocks are better if you do not have a lot of resources or time to prepare your tank.
  • Do not overload your tank with heavy rocks as this may crack the aquarium glass or the aquarium stand that your aquarium is supported by because it may not be able to hold the extra weight once the water has been added.
  • Always remember to clean any rocks or stones before adding them to your fish tank. Allow them to soak in boiling water for ten minutes to get rid of all the unwanted algae, bacteria, fungus, or parasites they may contain.
  • Add a level of gravel or sand before placing your rock in your tank to avoid breaking or cracking the glass.
  • Make sure your stones are secure in the substrate or the wall of your tank to prevent them from falling over.
  • Before and after the water has been added, be sure to check that all your rocks are secure enough, and will not break loose or move.

fish tank rocks

Types of Fish Tank Styles

There are two basic types of rocky fish tanks, but generally you can add rocks to any aquarium. The two main styles include the Ishigumi style and the Iwagumi style.

What Rocks Should I Use?

There are three main categories for the types of rocks we can use in our fish tank, which each have their own sub-category. They include sedimentary, igneous, and metamorphic rocks.

Sedimentary rocks include marl, limestone, sandstone, breccia, conglomerate, and shale. Igneous rocks that can be used in an aquarium include dolerite, gabbro, and basalt.Metamorphic rocks include quartzite, dolomite, marble, phyllite, slate, schist, gneiss, and hornfels. Depending on the biotype, all of these rocks should be suitable for a fish tank.

It is interesting to know that sandstone, granite, slate and basalt can be used for low or soft pH levels in aquatic water conditions and marble and limestone can be used when buffering is needed in hard water environments with high pH levels.

Other popular rocks that people use in their aquariums usually include lava rocks, which in turn can be used to fertilize the aquatic plants. Slate ages very well in fish tanks, but can have very sharp edges.Granite is also a really safe type of rock, but can be very heavy on the glass of your tank.


While adding rocks or stone to an aquarium is becoming a very popular trend, it is always wise to do a little research before purchasing or collecting random rocks. Make sure that your rocks are fish and aquarium friendly. If you have trouble with selecting your rocks or identifying them, you can ask your local aquarist for assistance.  Always clean any rock before adding them and if you have done all that you can do to ensure your rocks are safe, then add a twist with a rocky vengeance to your tank. They are guaranteed to make any tank look breath-taking.

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