I can't recall seeing any fish being named the "Armored Red Guard" but, if you mean the Red Armored Guard, they could be easily found in the Atheneum in Dragonspyre. They are the only sentinel fish there, and they are a Rank 1 Ice School fish. Just look for a shadow with spikes on it, sentinel fish will immediately go for your lure if they see it, when they get near your lure, immediately press the spacebar or press the invoke spell button, otherwise, they will steal your lure. Be sure not to use the scare away sentinel fish spell if you are trying to find it.
The ones I caught were right in the waters near the quest giver, but they are everywhere in Dragonspyre. They are the fish with the barbs showing above the water. I used a common (3) ice lure. The "trick" is to be extra fast reeling in. Good Luck