Choosing and Cleaning Aquarium Rocks

It would seem to be a simple task to find rocks for your aquarium, just go and pick some up. Not so! Unless you know what you are doing, “just picking up rocks” can be a disaster. If you happen to pick the wrong ones, rocks can change the water chemistry in your aquarium to the detriment of your fish. What do you know about aquarium rocks?

Rocks for aquarium

Your local aquatic outlet will provide a selection of rocks for both fresh and marine aquariums, so be sure to check with them that you have chosen the right ones. Bear in mind that waterworn rocks look much more natural than broken, angular pieces, and try to stick to one type of rock rather than mixing different colors and textures. If you want to build up a rocky structure in the aquarium, glue together cleaned, dry rocks with silicone sealant before putting them in the tank. This will prevent rock structures from falling down.

Unsuitable rocks

Avoid rocks that will change your water chemistry. Tufa is used in marine tanks and both tufa and limestone are also used in hardwater freshwater setups to help maintain water hardness. These are not suited to a tropical freshwater tank such as the one we are setting up.

Notes:

• Weathered limestone has natural fissures that create interesting textures in the aquarium, but should only be used in tanks whose inhabitants need harder water (such as rift lake cichlids).
• Rocks in shades of green and gray increase the range of color available.
• The dark tones of slate provide a dramatic contrast.
• Warm colors glow in the tank lights.
• The grainy texture and solidity of granite add “weight” to tank displays.

Placing the rocks

1. Carefully plan where you are going to place your rocks. They are heavy and you may need help to lift and place large pieces. Wriggle them down into the substrate until they are resting on the base glass to prevent fish from undermining them.
2. When you are satisfied with the position of the main piece(s), you can add the smaller ones until you have completed your layout. Remember to leave enough room to replace or service any equipment in the aquarium and avoid disrupting the water flow from the filter.

Creating stable rock features

If you are creating a cave-like structure with rocks piled on top of each other, it is essential that you place the base rocks safely. Fish are more powerful than you might think and it is not unheard-of for parts of a supposedly safe structure to move, fall, and crack the aquarium glass. Remember: structures must be stable.

Notes:

• Smaller waterworn pebbles can help to take the edge off larger angular rocks.
• If you were to accidentally drop a rock from a sufficient height, you could crack the tank. Make sure you have a good grip on it as you place it in the tank.
• Be careful when adding heavy rocks that you do not accidentally damage the equipment you have just installed.

Cleaning rocks

Rocks need washing: indeed, they need scrubbing. The amount of dirt that can stick to a seemingly clean rock is amazing, especially if it has deep crevices, such as this piece of weathered rock. Be sure to remove all dust, dirt, and pieces of moss or lichens to prevent them from fouling your tank.

Previous article: How to Choose and Prepare Aquarium Driftwood
Next article: The Water and Adding the Aquarium Water