Hi I have an established goldfish tank and I wonder if it is ok to take out the gravel and put in black pebbles. I want to do this for aesthetic view and to make it easier to clean. Will this kill my beneficial bacteria? I am almost positive the answer is that it's totally fine but I just want to hear some thoughts on this. Side note: my tank is slightly overstocked for goldfish which is why I am starting up an indoor pond soon to house my fish.