Can I add stones, rock or wood from my garden into my aquarium?

Outside of the artificial rocks designed for marine tanks, there’s no such thing as ‘new’ rock or stone. The rocks in your garden are millions of years old and have probably been lying around for a very long time. The biggest advantage to hardscaping sold for aquarium use is that you don’t need to be a geologist to know whether it’ll affect your aquarium water. It also has a known recent history and is free of any harmful chemicals which may have been used in your garden or lying in the soil.

If you are lucky enough to have chemically inert rocks of known organic origin, a few drops of a mild acid such as vinegar will tell you if there’s any calcium present that will dissolve and push up hardness or pH by fizzing, whereas an inert rock will merely now just taste of vinegar.

Wood can be a bit of a gamble although oak, beech and a few other hardwoods can be used safely if long dead and seasoned. The main challenge with these is their initial buoyancy and the fact that the softer portions of them can start to rot and cause problems. Most aquarium wood tends to have already aged past this stage, leaving the durable heartwood which is lower in soluble nutrients and tannins. As with rock, a certain amount of expertise is needed to identify safe options and chemical contamination cannot be ruled out entirely. It’s also worth remembering the value of deadwood as wildlife habitat and many specialists such as Stag beetles require it to survive – that magnificent fallen stump may be important to your garden bugs, despite being the ideal shape for your new layout. Of course, not all wood-eating animals are terrestrial and many of the L number plecs will appreciate access to soft, soaked hardwood which they soon reduce to wet sawdust.

As you can see as well as rewards, there are risks that are entirely removed by buying rather than foraging for your décor. Both rock and wood are generally items that last a very long time and can be seen as an investment, especially as every piece is different.