I think it might be a young fire eel. i'm not familiar with juvenile fires. I have peacock and tire tracks. This is straight out of Wikipedia and note the portion on juvenile coloring:
Physical description
The fire eel is an extremely elongated fish with a distinctive pointed snout and underslung mouth. The body is laterally compressed particularly at the rear third where it flattens as it joins the
caudal fin and forms an extended tail. It is part of a group of fishes called
spiny eels that also includes Tire Track and Peacock eels. The group gets the "spiny" part of its common name from the many small dorsal spines that precede the
dorsal fin. The frie eel's base colouring is dark brown/grey, while the belly is generally a lighter shade of the same colour. The pattern varies from fish to fish. Usually several bright red lateral stripes and spots mark the body. The red markings vary in intensity depending on the age and condition of the specimen. Usually the markings are yellow/amber in juvenile fish, changing to a deep red in larger ones. Often the anal, pectoral, and dorsal
fins have a red edging.
The name "eel" is a reference to the body shape; the fire eel is not a true
eel.
The fire eel can grow to a very considerable size in the
wild with specimens often exceeding 1.2
m in length. However, due to limiting factors in the captive environment they usually reach a maximum of around 55
cm even in very large aquaria.