something is feeding the cyanoto make it reproduce so fast maybe something from the transfer or something died.... since its a fish only id just keep battling it with water changes,and flow the usual and my little trick i tell everyone and they all seem to love it is take a pantyhose over a cup use a turkey baster to suck up mats of cyano and empty it into the pantyhose once your done you have a sock full of cyano and your down no water. i keep that stuff right next to the tank so i can suck it up as soon as it appears again
when ever my snails reproduced i would get little outbreaks of cyano and that was how i knew they were mating, at first they are so small i cant see them but the signs are there and with in days they are view able