Rocks from a creek
I have been wanting to add some larger rocks to my tank for decoration but my wallet has been suffering from my previous aquatic escapades. Instead of buying rocks, I decided to pick up some rocks from a nearby creek. Multiple posts have pointed out to check that the rocks are aquarium safe (they do not contribute to water hardness or contain heavy metals). I am going to test the rocks using vinegar for signs of rock that will increase the pH of my tank and also for shiny flecks to indicate if any metals are present. Aside from that, what other steps should I take in preparing the rocks for my tank? Most of the rocks were taken directly from the creek bed and contain little critters and other slimy matter. It has been said to boil the rocks/bake them although I read some horror stories of rocks exploding in the oven if they are saturated with water (I'm guessing mine are since they are directly from the creek bottom). Instead, I think I'll throw them in a fire outside and let them bake for a while. Other than that, would a thorough scrubbing and soaking them in a bucket of bleach make them safe for my tank? (water hardness/acidity aside) What other steps should I take? Do I need to be concerned about anything else regarding the effects of introducing rocks to my tank?
[My tank is still new, ~1 week old. It is a 29 gallon tank that I received secondhand (airpump and power filter are brand new). I have a basic gravel substrate, a piece of bogwood, 4 live plants, and a few goldfish still living (recent outbreak of ich has knocked off a few). The tank hasn't cycled yet (I don't think atleast). I plan on introducing tropical fish to the tank once it has cycled; specifically schooling fish such as tiger barbs and tetras.]
I boiled the Rocks I added to my tank, 20-25min., using 1/2cup of Aquarium Salt. They did not show any reaction to Vinegar before boiling. Rinsed them in Aquarium water after they cooled. Made 2 small caves for future inhabitants :wink:
Thanks for the reply. Instead of aquarium salt, do you think regular table salt would work? Also, did you glue the rocks together to keep them from tumbling? I have a few about the same size as the rocks you have in your tank but I also have a few large ones. Would hot glue or anything work at keeping some of the larger rocks from falling and hitting the glass should something knock them?
NOT speaking from experience here, but I have read that aquarium silicone can be used to glue rock together.
Aquarium Salt does not have any additives like Iodine! Salt for human consumption is often enriched with Iodine.
In terms of toxicity to higher organisms, the concerns vary considerably from organism to organism. Rainbow trout, for example, are quite sensitive to I2, with the LC50 (the concentration where half of them die) below 1 ppm iodine.
I did not glue the rocks in place. I placed them so that the bigger ones were on the bottom and smaller as they go up. I left about 3/4-1" behind all of them towards the back glass...then filled the voids with tank gravel so the bigger rocks cant fall against the glass :wink:
I have heard of silicone being used as well but I would imagine you would want to do that without fish in the tank.
I'm not going to add any fish capable of moving these rocks either.
Another thing to think about...placing them in the tank displaced approx. 1-1/2gallons of water.
I had one of my club members be kind enough to give me a big bucket of slate, he also gave me the idea to silicone it togather, works like a charm, just select 9-12 small pieces and do three sections 3-4 high then one large piece on top..instant cave.
Unfortunately with river rock, shiny flecks might not be a great measure of heavy metals. Also, I would recommend against boiling rocks, this can cause a rock to explode depending on what the rock is comprised of. The best way to determine what's in the rock is to contact a local geologist. They will know what the different rock types are, what they are composed of. For freshwater, avoid anything with calcium.
How would I go about searching for a local geologist? The nearest college is ~1 hour away. Any other locations I could check?
Thanks again for all the great replies!
I have just completed my month long trek to good aquarium rocks. Rock often times have MANY diffrent stages of geologic progression and composition in them, but, IMHO, after my research its not that big of deal.
With wet slimy rocks like that I would give them a good scrubbing and cleaning and then let them sit in some bleach water for a day or so. (remember to wash them good after this, and maybe let them sit in some water that has a double or triple dose of water conditioner, that will help neutralize any random chlorine that is around and hopefully react with any other nasty stuff).
I think it is important to remember that a lot of the "bad stuff" i.e. heavy metals are not easily taken up by the fish unless in their free ionic form. Water conditioners don't just magically destroy heavy metals or chlorine, they react with them and bind them up in a form that prevents them from being taken up by the fish's metabolic process'. Oxides for example, (rusts) are fairly difficult to produce toxicity. Remember though, that once you start getting high concentrations of H+ ion crazy stuff starts happening (i.e. keep your pH neutral or above )...
Anywho that's my two bits... Try searching for a very good article by Bob Wyllie called "Suitability of Rocks in the Aquarium"
also P.S. on the whole thing... I think its more fun and produces cooler rocks by getting your own!
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