btw, what is it that the chemicals do exactly? do they target the cyano specifically or does it target all bacteria and stuff like i heard? and how does it not come back afterwards?

i started getting this problem as soon as i got the tank back from someone in san antonio. because i had to transfer the sand from the broken tank into another tank, i think it messed something up. no matter how much i feed, its still there. im setting up a sump in the coming week in order to start adding better equipment in there