Friday, March 28, 2008

Cheap Scapes: Collecting Your Own Rocks

Who ever though they'd be paying good money for a rock when they started an aquarium? Yet many of us do. After discussing ways to save money while creating a beautiful aquarium in the last post, I touched upon collecting rocks yourself to use in your aquarium to save money. I've decided to continue the budget aquascaping theme with a post on collecting your own rocks to use in your aquariums. If you're lucky enough to live in or near an area that has appropriate rocks, this can be a great money saver and add a unique flavor to your aquascape. Sure, you'll get some strange glances as you lug a bag of rocks back home, but it's worth it!

It can be difficult to find rocks locally that "fit" into an aquarium. Some will just look out of place underwater. The best rocks are those found in or near water. Rivers, streams, and lakes are the best source. These rocks often have more rounded edges and will look more natural in the aquarium. Since they also are often worn smooth, you will have less of a problem with algae or detritus collecting on the rock. Finally, since they have been under water before, they are most likely (although not always) safe to put in your aquarium.

This brings up several important things to remember when putting rocks in your aquarium.
First and probably most important is the fact that some rocks just aren't suited for aquariums based on their composition. Certain chemicals contained in the rocks can leach into the water and play havoc with your water parameters. Some, like calcium carbonate or magnesium carbonate, will make your water hardness go through the roof as the elements dissolve into the water. Marble, limestone, coral, dolomite, or anything similar will do just that. While it's possible to live with rocks that impact your water parameters (Amano scapes often use such stones) in the long run, it just isn't worth it. Rocks with obvious metallic seams in them should also be avoided as they can also leach harmful substances into the water. A decent (although somewhat dangerous) method of testing whether or not a rock will dissolve into your aquarium is to put a few drops of acid onto it (strong vinegar or muriatic acid; be careful!) and see if it foams or fizzes after a few minutes. If it does, it likely contains an element that will affect your water parameters.

Second, rocks come from an outdoor environment. They can carry all sorts of dirt and substances on them that may be harmful to your aquarium's ecosystem. What I do is wash them thoroughly under running water with a mild soap to remove any loose dirt and oils. Then, I put them in a pot of water and boil them for a while. This kills any living things on the rock that I may not want in the aquarium. After the rocks have cooled they should be ready to be placed into your aquarium.

Using this knowledge, and a basic understanding of geology, it's possible to find unique and interesting rocks locally for your aquarium. Best of all, they're free!


  1. Is there anything in particular to look for when testing water parameters after adding rock found in nature?

  2. Mostly you want to check the water hardness and pH. A soft rock that slowly dissolves in water will affect the hardness of the water.

  3. I collected rocks and sand from a lake where my grandmom has a small house. When I flew home a kept the sand in my carry-on baggage. The lady in the sequrity check, who looked at the x-ray, in the passport control said to me she had never seen a picture like that and was wondering, out of curiosity, what I had in my bag. She wasn't much wiser when I told her it was about 15 kg of sand.

  4. What about collecting driftwood? Anything we should or shouldn't do? I want some new driftwood for my 40g tank, but don't want to spend the insane amount of money the LPS wants.
    Thanks for the tips!

  5. Thanks for sharing. Could you shall a little bit more on how do we "clean" the rocks from nature to minimize the sharp change in pH and hardness, or even any possible infection?

  6. Hope you write another blog soon. We miss ya!

  7. I realy enjoy collecting rocks for my aquariums but I use some different methods. For the nanos I a use a hammer to break a bigger rock into smaller pieces - these will have the same texture and color and will give you a more natural look; you can easily find them on a river, the trick is finding a big rock. For the larger aquariums I try to get the rocks from the rocky parts of the mountains - never rivers -, usualy mountain tops or at least 1000m high. I don't like collecting directly from the river because it's hard to get 3 or more rocks that have the same color and texture.

  8. Railroad tracks can be a great place to find rocks. Where I live in central texas we have mostly limestone which is only appropriate for cichlids. I have picked up nice granite pieces for nano tanks there. Big selection.

  9. I added some semi precious stones to the bottom of my tank. The shop checked with the supplier and they were hand polished with no chemicals. There was only one fish in the tank at the time and it died. I had tested the water the day before and tested it again but the results were all fine. Could the stones have caused the death?

  10. I want to build a scaped 55 gal and move my discus into this tank I want to use a good substrate. Is there a live sand for freshwater that won't have a high ph

  11. I put some softball sized river rocks in my aquarium from the mountains west of me, what seemed like good stable granite but it gradually raised the GH up to around 15, it didn't raise the KH though.

  12. I live in Sydney Australia and i get my rocks from a river in Kangaroo Valley all shapes, sizes and color and 100% free I'm going back there to get a lot more my 6ft tank and they didn't seem to raise to Ph lvl any so that's a bonus.

  13. Hi, just wanted to add something about your test for calcium carbonate. Something I picked up in geology class a couple of years back.

    They didn't want us to handle highly-concentrated acids in the lab so they had us take a small metal scraper and lightly scratch a small area on the rock, just enough to create a small amount of surface dust. Once you have the surface dust, it will bubble with common white vinegar if calcium carbonate is in the rock.

    This method should be safter and more accessible for most people.


    I love the site.

  14. I have tried twice and both times I use natural rock it builds a alge like substance on the rock. Any pointers?


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