Impact Of Found Rocks On Water Parameters?

[BeckyCats]

Hi All! I am setting up a new 55 gallon aquarium and am wondering about the impact that rocks will have on my water parameters (if any). My water is soft and I want to keep it that way since I want to keep soft-water fish. I believe the rock is granite with varying amounts of quartz and iron in it. I am leaning towards just skipping it and buying fake rocks just to be safe, but it doesn't hurt to ask.
Thank you!

 

[fluttermoth]

The best way to check it, is to leave out two containers, one with some of the rock in it and one without. Test both after a week or so, for pH and hardness, and you'll know if the rock is affecting your water or not

 

[BeckyCats]

Thank you. I'll have to try it.

 

[SherLar]

   If you're certain they're granite, you should be fine. However, if you think it has iron, or any other metallic components, I would skip it. Metal in a fish tank is never a good idea. 
   Otherwise, most sedentary rock won't dissolve in water, and as long as it's well-cleaned (I boil found stones to be sure bacteria is killed off), and has no limestone, shale, basalt, or chalcedony, they're usually safe to add without altering water parameters.

 

[BeckyCats]

Thank you! I'm not 100% sure it's granite. I know some geologists though, so I'll ask them what it is.

 

[StevenF]

 
 
Test both after a week or so, for pH and hardness, and you'll know if the rock is affecting your water or not 

I would also tet for KH..So test for PH, GH, and KH.  If there is minimal change the rock is probalby OK.  

 
 
 If you're certain they're granite, you should be fine. However, if you think it has iron, or any other metallic components, I would skip it. 

All rocks including granaite have metal oxides.  What you however need to know is how much of the rock is water soluble.  If very little of the rock is water soluble it will be OK.  

 

[BeckyCats]

Thank you!

 

[Akasha72]

you could also try dripping white vinegar onto the rock. If it fizzes on contact it's not safe to use. 

 

[scandie]

I think you should speak to your geologist friend(s). Water soluble surface contaminants will show up in a short time.  Even granite when exposed to acidic rain will dissolve, but I think we are talking about hundreds or thousands of years.  Will it make a different in the short time your fish will be alive?  I don't think you will be putting in acidic water intentionally.  I agree with the comment re bacteria however, but let us know what the geologist tells you.

 

[BeckyCats]

I tried the vinegar and there was no fizzing. I'll try the geologist test tomorrow (ha!) and if it's questionable there, I'll try the week-long bucket test.
 
I scrubbed all the rocks with hot bleach water. When I was a kid, we brought home a river rock and put it in the tank and became so overrun with snails that I believe we ended up getting rid of the tank. And believe me, my mom scrubbed that rock first, so I know that snails and other yucks can sometimes escape a mere hot water bath. I read that some rocks can explode or split violently when boiled, so I didn't go that route. Soaking in a weak bleach solution seemed to me to be the safest course of action. If I do put it in the tank, I'll soak it in water with dechlorinator first,  to get rid of any bleach residue.

 

[Akasha72]

yes, rocks can explode if boiled. So glad you knew not to try it. It's so dangerous. I have slate rock in my tank and they are fine

 

[BeckyCats]

I've had some of the rocks sitting in water in a very small bowl for several weeks now. I have not changed out the water, just keep adding more as it evaporates. I tested the water and everything is the same except the gh went from ~30 to ~40 (one slight color change on the test strip). This is using test strips, so who knows on the accuracy. The kh stayed the same. I am comfortable that the rocks will have minimal effect if any, in a tank. One great side effect is that the rocks have grown algae that my gobies think is delicious. I put one of the algae-covered rocks in the aquarium, and they had it cleaned when I came back a few hours later.

 

[Akasha72]

glad it worked out for you

 

[tunagirll]

Granite is generally a very inert rock, if you're not sure post a pic

 

[BeckyCats]

On a hunch, I talked to a geologist at work and asked whether it were possible that the increase in gh could be due to the evaporating water rather than the rocks and he said absolutely. The total dissolved solids do not evaporate out, so since all I was doing was topping off more water as it evaporated, the gh or tds was increasing because that stuff was just building up.