lol if you are talking monster or predatory fish, we have all done this. I was particularly bad at underestimating what catfish can swallow. I dont know how many fish I lost to my pike cichlid, bichirs and catfish. Size is always important. Even peaceful fish will aggressively hunt down other fish if they are small enough. For years I lost school after school of neon tetras until I finally caught my botia hunting.
To save you future headaches, if you are ever not sure about size compatability use a grow out tank. With monster or predatory fish, there will always be a small risk even if others on MFK have success
To save you future headaches, if you are ever not sure about size compatability use a grow out tank. With monster or predatory fish, there will always be a small risk even if others on MFK have success