I recently purchased 2 guppies from my lfs. I noticed one had torn fin was looking skinny and his gills are red the other has clamped fins and red gills I dosed my whole tank with maracyn and paracleanse today. The tank has been established since July. My question is should I expect these medications to completely crash my cycle. I do not have a quarantine tank or I would have used it I know I should have one but don't have room for one I learned my lesson on buying fish without doing a proper inspection of them before hand. Also if my cycle does crash I would need to perform water changes or can I add prime in not feeding during this time to prevent a spike in nitrite or ammonia.