What would be the best way to garuantee rocks from the garden aren't going to contaminate the fish tank at all, i was planning on putting them in a drum full of water for a few days and tipping in a bag of salt to kill any nasties in there, but what other ways (other than boiling) would be good to make sure there are no pesticides or herbicides on them???

Do you think a bottle sterlising cleaner would work, it says its a chlorinated cleaner, and used for sterlising bottles for home brew, or should i just stick with lots of salt.

I would think it would work but wouldn't salt be cheaper?

Unless it is some sort of porous rock, it will not have absorbed any pesticides so I would think pouring boiling water over it and/or salt, would suffice

Why not just use bleach and give it a good rinse afterwards.

Personally I wouldn't bother trying to clean them, why would something that normally lives in the air be a problem underwater?? I just give rocks a scrub to remove any dirt and put them in.

me to i just give a good scrub in hot water and stick em in i have 5 tanks with rocks from outside and havent had any probs

I was going to bleach them over night but we have no bleach, and supermarkets aren't within walking distance. I've been letting them sock so might just pour boiling water over them and stick them in a tank with a couple of guppies and see what happends.

I have only ever just scrubbed rocks before putting them in a tank.

I was in Pak n Save Mill St the other day and by the Janola etc there are bottles of an ammonium chloride bleach that should be ideal for cleaning - the ammonium will get eaten by the denitrifying bacteria. Sorry can't remember the brand name but it was a clear bottle about 1 litre maybe 750ml.