rocks to avoid in a freshwater tank?

[royta]

Are there any types of rocks one should avoid using in a FW setup due to them affecting water parameters?

My parents are coming to town and they have a ranch loaded with lava rock. My parent's place is about 20 miles as the crow flies to the peak of Mt. Shasta. I spent my younger years stacking lava rocks in piles along the fence lines. I thought the rocks might look cool and give plenty of nooks and crannies for Oto's to keep clean.

Thanks.

 

[Mogurako]

Lava rocks should be just fine in a tank they are completely inert and shouldn't affect the water. I have used them in my tanks before but you have to clean the super well because the carry allot of junk in those little holes.

 

[subliminalanarchy]

I've heard that some of them can leach weird metals into the aquarium so it's not usually recommended. I have like 80 pounds of lava rock in my 55g though, and I haven't ever had any problems. They look really nice and provide a ton of natural hiding places.

You can always pour some vinegar on them to see if they are calcerous. If they are calcium based the vinegar will bubble on the rock and that means it will raise your pH.

The best thing to do would be to rinse them off really well, let them soak for a while and then test the water they're in to see if the rocks are affecting the readings at all. Then soak them in water with a little bleach for a day or so. After that, soak them in regular water with a bunch of water conditioner for an additional day before putting them in the tank.

 

[Morgie]

I wouldn't recommend using lava rocks. They are bound together very loosely and have a tendency to dissolve in water.
/Maybe/ if you soak it and scrub it several times it will be safe to use.
It will probably raise your water hardness levels and may affect your pH, I'm not totally sure, but I personally wouldn't use it. I have lava rocks for a water plant I have in a bowl on my desk and ever time I water it (the rocks have been soaked for years) the water turns dark red and fragments of rock come floating to the surface and I have to clean it out. I'd just go with another kind of sedimentary rock just so you wouldn't have to deal with the potential risks/maintenance required to keep lava rocks in aquaria.

I am a geology major, if that makes a difference haha. There are plenty of other great rocks to use in your tank, but a lava rock is better off in the garden.

 

[Mogurako]

I think it also depends on the type because there's some that's more porous and crumbly an others that are quite soild. I'd most defiantly test it in a bucket of water to test it first.

 

[royta]

I wouldn't recommend using lava rocks. They are bound together very loosely and have a tendency to dissolve in water.
/Maybe/ if you soak it and scrub it several times it will be safe to use.
It will probably raise your water hardness levels and may affect your pH, I'm not totally sure, but I personally wouldn't use it. I have lava rocks for a water plant I have in a bowl on my desk and ever time I water it (the rocks have been soaked for years) the water turns dark red and fragments of rock come floating to the surface and I have to clean it out. I'd just go with another kind of sedimentary rock just so you wouldn't have to deal with the potential risks/maintenance required to keep lava rocks in aquaria.

I am a geology major, if that makes a difference haha. There are plenty of other great rocks to use in your tank, but a lava rock is better off in the garden.

I guess using the term "lava rocks" could describe a gazillion different type of volcanic rocks.

The lava rocks I'm talking about are very dense, only have holes about 1/4" deep at best, and are absolutely not bound loosely. Mt. Shasta also has less dense red lava rocks that came from cinder cones on the side of the volcano that are easy to smash and break up. Not the same stuff as the lava rocks in the Big Springs area of Siskiyou County, CA. They are very heavy and are very difficult to break apart.

When soaking the rocks in tap water, I'll check water parameters and see if there is any change.

 

[jcolon]

In regards to "Lava" rocks, the correct term for them are Igneous Rocks which are a wide range of rocks that form when Magma (ex. Granites) and Lava (ex. Scoria) cool. Most lava rocks I see in tanks resemble scoria. Some igneous rock are Iron and Magnesium Rich and are usually darker in color and very dense, while others are Silica Rich (Granites), usually lighter in color and density.

I teach Regents Earth Science so I agree that Carbonate rocks like Limestone Dolostone and Marbles will raise your pH ... so avoid them if you want soft acidic water. A vinegar or some other acid is a good test ... if it bubbles, it's a carbonate.

I finding Slate is a good rock to use, generally doesn't contain metals and it is sturdy enough to submerge and hold weight ... plus you can use them to make caves!!