I get all of my tetras and schooling fish form petco because my LFS does not carry tetras and fish in that area. Every time I get fish from there I almost always get ich, and it is rare for me not to get ich when I buy fish from petco. My question is when I get the fish from petco, should I just treat them form ich even if they don't show sighs of ich? If they don't have ich and I treat them for it could it hurt them?