Rocks in my first aquarium

[wwomack]

I just bought my first aquarium. It's a 29 gallon with a Penguin 200 filter. I've got gravel, two fake plants (need more) and a few rocks that I found in a mountain creek. Tuesday I put 4 small tiger barbs in there and am currently cycling the tank with them. The tiger barbs have been in there for 3 days and are getting more comfortable with their surroundings now. I need to put a solid background on there and add some more cover for them.

My concern/question is about the rocks. The more I look at them I'm worried that there is rust on them. Initially I just thought it was a neat orangish color but now I'm not sure. Do other people also think it's rust? If it is rust, will the rust be bad for the fish? The three pictures below show one of the three rocks that I'm concerned about. The other two rocks in the middle picture I think are okay. They don't have any of the orange color on them.

 

[krazymom]

I recently found some nice rocks with orange and red on them and thought the same thing. I was advised here to put acid on the rocks and if it fizzes it is leaching minerals and if no fizzing it is safe. Mine didn't fizz at all. Then you have to make sure to rinse the heck out the rocks to get all the acid off. I used a muriatic/ nitric acid mixture that was in my hubby's gold testing kit. Maybe pool acid would work if you have that. So far my fish have been totally normal and it has been about 2 weeks or so.

 

[wwomack]

Hmm...I didn't do the fizz test. I did soak them in a bucket with water and some bleach for a few days though like I saw recommended. I figured that would kill any living offenders that might be in a nook of the rock.

 

[greenmaji]

vinigar can be used for the test, but muratic acid will work better and is available at ace hardware..

 

[krazymom]

My bet would be that they are fine cause my rocks have lots of deep red on them and also orange like yours and they weren't leaching according to the acid test.

 

[wwomack]

I decided to go ahead and remove the rocks. It was making me paranoid about what they might be doing to the water.

I think the orange is rust on the metal in the rocks. I looked outside on the patio where the rocks had sat before I cleaned them and prepared them for the aquarium and there were orange rust spots on the concrete.

I removed the offending rocks but left the couple in that had no rust and seemed to be of a different type. I added a fake driftwood/root thing from the local petstore and some more fake plants so I think the aquarium is looking okay without those rocks now.

My current setup (except I've now added a black background):

 

[Biotoper]

If a rock has iron, it can rust (it may not always be visible on the surface). The acid test should work, as iron oxidation should increase with more H+ ions to carry away electrons. But I think your patio test is better, assuming it rains.

All that said, some aquarium substates have iron in them (plants need it), so I don't know if rusty rocks are a big concern - don't know enough about the chemistry of different iron molecules and how they interact with plants and fish.
I haven't heard anything about rust before (at least in rocks - metal equipment is a different issue), compared to all the information about being carefu not to add calcareous rocks.

 

[greenmaji]

your just supose to be carefull with the use of Fe stone in your aquarium.. an overabunduce of Fe can be the underling cause of some algaes... It could become toxic at some level but Im sure you would have to be dosing it to get there..HTH