? about rocks i just bought

[TaTeR ToT]

ok, im not sure if this is the proper forum for this, but here goes.

i just bought 2 gray rocks, they weigh about 20lbs each.
anywho, my question is they have this residue, its like rust almost, its rusty in color, but i dont think its actually rust.
because, there was no metal on or around them.
they are awesome, and i really want to use them in my 125g, but im afraid of this residue.

heres a couple pics of the 2 rocks -





its the rusty colored stuff.

[TaTeR ToT]

Anybody have any advice on this?

[RMD55]

Could be natural iron oxide (rust) in the the rock. A couple of this you might want to try is 1. just soak them in water and see if it stains the water 2. wash the rocks with muritic acid, pools supplies have it to balance the pH. Dilute about 1 cup per gallon does not need to be exact and make sure you add the acid to the water, diluting produces heat the other way around causes problems. Use a plastic container, rubber gloves are a good idea and if you get any on you rinse for at least 15 min in running water baking soda helps too. If the rocks fizz alot in the acid they may not be the best for tank use and make sure that they are well rinsed before using.

[rrocket2002]

I use to use sprite or 7-up to clean rust off my bike when I was a youngin. Sort of fizzed a bit. I wonder if that would work on this?

[RMD55]

All that said they look great.

[RMD55]

It's the phosphoric acid in the soda that cleans the rust. I forms iron phosphate which as we know can cause problems with algae.

[TaTeR ToT]

well, the stuff comes off on yer hands, so i am gunna scrub one with a brush under running water, if that takes all or nearly all of it off, then i will assume that it is not part of the stone, but just a residue, i will update with the results as soon as im done.:)

[TaTeR ToT]

well, the brush took some off, but it seems to be on there really good, my brother in law said it looks like lime, if it is lime is that harmless, cause i dont think i can get it all off. i does kinda seem to be part of the rock:(

[TaTeR ToT]

i dont really want to bother with acid.
the thing that really is bugging me, is that i dont know exactly what the heck it is:|

[TaTeR ToT]

any other thoughts?

[TaTeR ToT]

bump

will iron oxide hurt the fish?
is it safe?
its not like the whole rock is made of the stuff, itslike a thin layer.

[Darbex]

I am not a geologist but more than likely it is embedded in the rock and you will be able to get the stuff at the top layers but not all the way through. I do not recall what causes it anymore I do think it was Iron Oxide but could be wrong but as long as you gave it a good scrub it should be fine. I have some on my black granite that makes it look cool and natural and I have had no problems with it and my Discus.

[TaTeR ToT]

cool, so i'll give it a good scrubbing again tommarow.
thanx for the help everyone.

[RMD55]

If you don't want use a strong acid you can use white vinegar.

[TaTeR ToT]

aight, i will try white vinegar,
so like if it fizzes, its no good?