Originally Posted by LouiMon
I bought white gravel for my tank but I'm starting to dislike how bright it looks so I think I want to get black...
Would I be able to switch it out without screwing up my cycle or would I have to start over?
Hard to say without knowing the dimensions of your tank and size of filter you have.
If it's a longer tank, that means you would have more substrate, decor, and other "things" that provide a breeding ground for good bacteria. Taking that in to account, as well as the size/type of filter you have, you could possibly have more bacteria on the substrate, decor, walls of your aquarium than in the filter. In which case, you would risk interrupting your cycle.
That would be the worst case... And even then, I can't imagine it would take too long for the bacteria to restabilize since a lot of it is still in the filter and some on the glass and decor. Try not to scrub the glass, and if youre keeping your existing decor, maybe fill a bucket with old tank water and put the decor in that bucket until you replace the gravel. That'll keep the bacteria wet and happy for a few hours at least.