Firstly the product claims years of scientific testing but does not say by whom nor is the data published. If it isn’t published and subject to review then it doesn’t exist as far as I am concerned.
Secondly the explanation given for its operation is gibberish.
From the screed: "Dog Rocks are a paramagnetic igneous rock. When this type of rock is immersed in water, the paramagnetism creates a magnetic field within the water causing a change in the ion exchange. This in turn diminishes the nitrates that are found in the water (a minimum amount) so when the dog drinks this water, less nitrates are being absorbed into his system and therefore less are coming out in his or her urine. "
- Paramagnetism is very common in the environment, there is nothing special about it.
- A paramagnetic substance does NOT generate magnetism, it is weakly attracted to an applied field. The only applied field here is the earth’s magnetic field which as magnetic fields go is extremely weak.
- “Changing the ion exchange” has nothing to do with paramagnetism. The rock may emit or absorb ions, or both, but this is unrelated and with an insoluble igneous rock the amount will be tiny - not to mention irrelevant (see next point).
- Lastly the key point: it is said to work by reducing nitrates in drinking water. This is absolute nonsense because the amount of nitrates dogs get from drinking water is somewhere between nil and miniscule. The vast majority of nitrogen compounds in dog’s urine is from their kidneys, that is what kidneys do, remove these compounds from the blood.
You can’t do much about preventing mammals from excreting nitrogen compounds in their urine, if you stop feeding them protein (where those substances come from) or stop their kidneys working they will soon die.
Putting rocks in your dog’s water will achieve only one thing - waste your money. Although it might annoy your dog. This product is a dead set shonky. The vendor ought to be prosecuted for misrepresentation immediately.