I think you may still see cyano
in the furture, taking out the one rock most likely won't stop it. Besides feeding also look into leaving your light on for shorter periods of time and determine if you have too much/not enough flow. I had a bad breakout of cyano
in my tank. I did everything I could to not have to medicate the tank but in the end sometimes you just have too. If you don't see it anymore without the rock then good job. But if it does come back I used cyano
solution , just one tiny treatment followed by a water change the next day and I have had zero cyano
in my tank for months and before that my whole tank was covered. Oh and I'm sure your fine just removing that one rock in terms of it "bacteria"