Is this rust on my rocks? My grandpa got these rocks for me from his backyard but I think theres rust on them. Can I use them in my tank?

[DoubleDutch]

My understanding is that iron is most toxic when it is dissolved in water. Iron oxide is typically not water soluble. So if you monitor your iron levels and they stay below 1ppm you should be OK.

I tend to agree with Steven. To my knowledge there won't hardly leak any iron into the water cause of the oxidation and the layer caused

 

[Colin_T]

You guys have said that its prob iron oxide which is good for plants so could I use this in maybe a plant grow out tank?

Yep. Just monitor the iron (Fe) level in the water. The rock might release lots but it might not release any. Monitoring the iron level will let you know if any is coming from the rock.

 

[PheonixKingZ]

Yep. Just monitor the iron (Fe) level in the water. The rock might release lots but it might not release any. Monitoring the iron level will let you know if any is coming from the rock.

That’s the issues with rocks, they are a loose cannon. It could release a ton of iron, or barley any iron.