No need to apologise, this forum is here to answer questions and we all ask them!
The thread linked above by @corylover5 explains the life cycle of ich. My understanding is that it is attached to the fish, then it forms cysts that fall off into the substrate, and finally more ich hatches out of the cysts and reattaches to fish. It can only be killed when it hatches out, not when it is on the fish nor when it is in the cyst.
Keep posting and good luck.
The thread linked above by @corylover5 explains the life cycle of ich. My understanding is that it is attached to the fish, then it forms cysts that fall off into the substrate, and finally more ich hatches out of the cysts and reattaches to fish. It can only be killed when it hatches out, not when it is on the fish nor when it is in the cyst.
Keep posting and good luck.