Can you put marble rock in goldfish tank?

Yes, you can put marble rock in a goldfish tank, but you should consider a few factors first. Marble is calcium carbonate, which can raise the pH level of the water, potentially leading to an unsuitable environment for your goldfish. It's essential to monitor the water parameters regularly to ensure they remain within safe levels for your fish. Additionally, ensure that the marble pieces are smooth and free of sharp edges to prevent injury to the goldfish.