I have a 6"slate tile for my knife to hide behind but I'm to one most likely to knock it over, also the water pressure is probably more stress on the glass than a reasonable rock would be.
And if your fish thrash around enough to knock rocks over I would be more worried about them getting squished or injured and not add anything to the tank they could knock over
And if your fish thrash around enough to knock rocks over I would be more worried about them getting squished or injured and not add anything to the tank they could knock over
