Way too many to list! you can test rocks with hydrochloric acid. If it fizzes, it leaches!

 

Most basically:
Any rock that is limestone, calcite, dolomite or related will leach mostly calcium and magnesium carbonates. Many rocks are in this group with lots of names. Some are harder than others, so leach more slowly. Others are so soft you can practically see them melting in the tank, especially if the water is kept on the acidic side.

Most harder rocks like quartz, granite, basalt and lava tend not to release minerals. However, sometimes these rocks can have veins of softer minerals in them. Then the veins might dissolve over time, but the main rock does not.

The easiest way to tell if a particular rock will leach minerals under your conditions will be to test.
Set up a jar of water with tap water or whatever water you will be using in the tank.
Add whatever additives you will be using in the tank.
Test this blend to get a base level. What is the water like before you add anything.
Then add rock samples. The finer they are broken up, the more surface area, the faster you will see results. If you have to break up the rocks wear eye protection! Rocks can chip and fly when you hit them with a hammer.

Test for all the aquarium tests that are available such as:
TDS: Total Dissolved Solids will let you know SOMETHING is in the water, but won't tell you what it is.
GH: Tests Calcium and Magnesium.
KH: Tests carbonate and bicarbonate.
pH: is not actually testing minerals, but might change to let you know something is going on.
Other tests based on what kind of rock you think it is: Iron, Phosphorus, Calcium, and whatever other tests you see.
There are some good web sites that can help you find out what the local rocks are in the hills near you, and can help you ID rocks from elsewhere. You could try posting pictures here, too. Explain where you found the rock.

 

Granite really shouldn't be leaching anything...

And any rock that will leach/dissolve, will do so quicker if there is more surface area.

A 1 lb chunk of limestone will dissolve a bit, 1 lb of limestone gravel will do so quicker, and 1 lb of limestone dust/flour will do so even quicker yet..

In addition to what Diana posted, you want to avoid anything that is a heavy metal ore, or an evaporite (gypsum, etc.), but these are a tiny minority of the rocks you will likely run across. Most rocks are going to be fairly boring old silicates.

 

Sorry, but I need to hijack this thread. Has anyone ever seen this kind of rocks before? Know what they are? Know if they're safe?

 

could be a mica schist.

 

Smeagol, Are your rocks super hard, or are they flakey and leave sparkly specks on your hands when handling them? They are definitely metamorphic rocks based on the foliation (parallel alignment of mineral layers or banding of different colored minerals). If the rocks are super hard, they're most likely "gneiss". If the rocks are more soft, flakey, & leave sparkly specks on your hands, I agree with jrh and would say the rocks are a "mica schist".

 

Yep, they are definitely flakey and leave sparkly specks all over the place. Mica schist it is! Thanks for helping me id these rocks! So then, is mica schist safe to put in the tank?

 

I think it should be fine. Most metamorphic rocks are inert (marble being the common/glaring exception).

Might want to wait till jrh or Ebeth check back in, as they both seem to be a bit more reliable geology-wise then I am.

 

No, you're better than I am, Lochaber.

I can't think of anything that might be in there that you'd want to avoid, unless maybe it contains pyrites. I don't see any problem with the softness of the stone, because I agree with Locaber in that it's probably inert.

Personally, I'm waiting for Ebeth to chime in.

 

Smeagol, I, personally, wouldn't put them in my tank. Schist is very prone to mechanical weathering, meaning the water will get in between the soft foliation groves and likely split them apart over a short amount of time. Mica schists are weird: micas aren't exactly clay minerals, but they can act like them. They'll get all over your tank, some clays are "swelling clays", etc., and will definitely cloud your water. Not to mention the possibility of metallic minerals in the schist, such as pyrite (shout out to jrh), blah, blah, blah. If it gets all over your hands just by touching, imagine what it will do to your tank. Sorry, I could go on & on & on. I'm sure you figured out I'm a geologist (who talks way too much). DON'T put them in your tank! Happy planting! Ebeth

 

smeagol, i, personally, wouldn't put them in my tank. Schist is very prone to mechanical weathering, meaning the water will get in between the soft foliation groves and likely split them apart over a short amount of time. Mica schists are weird: Micas aren't exactly clay minerals, but they can act like them. They'll get all over your tank, some clays are "swelling clays", etc., and will definitely cloud your water. Not to mention the possibility of metallic minerals in the schist, such as pyrite (shout out to jrh), blah, blah, blah. If it gets all over your hands just by touching, imagine what it will do to your tank. Sorry, i could go on & on & on. I'm sure you figured out i'm a geologist (who talks way too much). Don't put them in your tank! Happy planting! Ebeth

Rats. I've actually had these rocks in my tank for about a week now. I'm going to remove them immediately. Do you think there's any permanent damage done?

What about the rocks that are commonly sold in fish stores as "petrified wood"? Is that stuff safe to use? I have a little bit of it that I could use to replace the mica schist? But it has a very clay-ey feel to it... Would I just be trading one evil for another?

 

I got some. Me abd happi are doing a test to get exact ppm's of calcium and magnesium over a week in r/o. We will have results on a few days. The point of the test is to see if we can get an exact weight of rock per gallon to achieve 100ppm tds over a weeks time - minus the 20 percent water change. And get a 2:1-4:1 calcium to magnesium ratio.

I currently have shrimp stones leeches Calcium and Magnesium Carbonate
Cherty dolomite

Some limestone leeches calcium no magnesium

Acid treated or untreated to remove unwanted dolomite veins. In the for sale section.


Sent from my PC36100 using Tapatalk 2

 

The rock in the middle composed mainly of heated and shaped silica should do fine in the tank, though

 

Smeagol,
No worries! If it's only been a week, you're probably ok. I'd do a water change and just clean out your filter. You're fine.

Yes, petrified wood it great. Petrified wood goes through a mineral replacement called silicification. There's no organic matter left after this process. Silicification just means that everything has been replaced by silica, which is extremely stable and resistant to chemical and physical weathering. It would take 1,000's of years or more to weather away silica based objects, unless your pH is caustic, like 11.5 or 12!
Happy planting! Ebeth.

 

I removed the mica schist, completely drained all the water, and did a total re-scape using the small amount of petrified wood that I bought on a whim a few weeks ago. I had planned my entire aquascape around the mica schist even though I was suspicious of it from the very beginning. The people at the fish store couldn't tell me its name, and they couldn't even find it in their supplier's catalog to order more when I asked them to. I should've known right then to stay away from it. My guess is the fish store's supplier sent it to them by mistake.

The petrified wood looks terrific in terms of color, but it's proportionally too small for my tank and so it looks kinda pathetic... And yet, somehow I like this new design better. I think I did a better job of arranging the plants this time, despite the inadequacy of the rocks.

 

Smeagol, I'm really happy you like the design better (despite the size of the petrified wood). You can never go wrong with silica, or quartz, based rocks. When you think about it, it's no different from the quartz sand or quartz gravel we put in our tanks. I'm super happy it worked out, no damage was done, you acted quickly, and you're pleased with the results!
Sounds like a great ending! Happy planting! Ebeth

 

Thanks Ebeth! One more question: Are you telling me that the rocks called "petrified wood" that are commonly sold in fish stores are actually real petrified wood? As in, these rocks used to be tree branches millions of years ago. I thought it was just a gimmicky name used by the fish stores, a marketing ploy to sell some cheap rocks that look faintly like wood at elevated prices.

 

Could be either way. Some rock does look enough like petrified wood that they could get away with that.

 

Diana's right. Some striped rocks may be misidentified as petrified wood, but actual petrified wood is real wood where the organic stuff has been replaced with minerals, typically silicates. The resulting petrified wood should be just as hard and inert as quartz.

Yes, that's exactly my point. It begs the question... How does one know if one is buying actual petrified wood or just some random rocks that look like "petrified wood."

 

Diana's right. Some striped rocks may be misidentified as petrified wood, but actual petrified wood is real wood where the organic stuff has been replaced with minerals, typically silicates. The resulting petrified wood should be just as hard and inert as quartz.

 

Diana & jrh are both right!

It could be a gimmick, but it really depends on the local pet store. I don't shop for rocks at the big chains stores. IME they don't know much in the rock department. Some stores do try to sell gimmicks for a $.

I shop at a mom & pop pet store, and I trust what they sell me. But, yes, you could actually have a million year old tree.

Petrified wood is extremely dense, so it will feel really heavy compared to objects its size, it will look like wood, it won't be very smooth, it will look "crystalline". Pick up a jeweler's loop. You can get them online for really cheap (meritline dot com).

I think you'll have fun looking at things more closely.

Seems like Diana and jrh have a ton of knowledge, too. Very cool!

Ebeth

 

I have a question for the group, but not really about rocks. I hope that's ok!

In my 10g tank, I have black Flourite substrate and a white sand 'path'. I had an green string algae problem in the white sand path, so I vacuumed all the sand out.

Here's the question: Instead of replacing the sand with more sand, can I make the new 'path' out of wood?

I'm thinking of making a plank path out of tongue depressors, so I don't have to deal with the black Flourite mixing with the white sand, etc. Will the wood attract algae, will it rot, should I seal it, etc?

I'm not sure how to insert a link to my tank, but it's on the first page of the 6-10g tanks under Ebeth.

I'd appreciate any feedback!

Thanks, Ebeth

 

Wood of any sort will eventually rot in an aquarium, or get eaten by Loricariads.

Why not make a more rustic bridge or path using the hardest wood you can find, and make it out of twigs perhaps 1/4"-3/8" in diameter. It will look like a rustic log walkway, and will last a lot longer than tongue depressors.

 

Diana,
That's a great idea! I never thought of that, and it would definitely look better than tongue depressors!

I appreciate the advice!

And Smeagol: thanks, too! I think it's a great idea. I started the tongue depressor thing, and it looks ridiculous anyway!

Ebeth

 

That's a seriously cool tank, Ebeth! I second Diana's idea of using twigs. I think it would really compliment the rest of your design.

 

I want the path to look like the one in the attached photo.

 

I have a piece of mopani that you might be able to trim to fit (just boil the hell out of it several times or your tank will look like tea), and I also have a bunch of blue/grey slate chips. The largest pieces are probably 2" planks, the smallest are maybe dime sized chips.

You're welcome to either or both if you think you can work with them.

 

I think using small stones to try for a stone walkway/paved type effect might be easier and more stable. The wood pieces, since they are so small, would be likely to get out of place without some sort of anchoring/attachment. I think...

Have you completely removed the sand? Just wondering if you disturb/turnover the sand during your regular maintenance, if that could help slow/obscure the algae?

 

Lochaber,

Yes, I completely removed all of the white sand by vacuuming it out. I first tried to work with it by manually removing it the algae, but it just made a mess and spread everywhere. Thanks for the advice. I appreciate it!

Jrh,

Thanks for the offer. I actually just got in a shipment of driftwood, but I agree, and think it will be moved around a lot. I think I will go with the stone path. I have literally boxes of rocks due to my profession. But I seriously appreciate the offer of wood & rocks and the advice!

The tank looks so weird without the path!! I think I'll tackle the path this weekend. It will definitely be less maintenance without the white sand. Thanks everyone!

Ebeth