fire eels come from asia, usually a flat black color with red stripes, running length wise of its body. A pH level from acidic (6.5) to just above neutral (7.4) is fine.
Use a fine-grained aquarium gravel, several pieces of driftwood would be nice,do not use any abrasive materials as substrate, because Fire eels are burrowing fish, The scraping of the eels belly or fins can lead to bacterial or fungal infections.
Keep your temps in the lower 80s as they prefer warmer waters to be very active, if your temps are cool they will simply hide most of the time.
They prefer live foods such as bloodworms, and brine, but yours may hve already been acclimated to frozen, which will make it much easier for you.
Good luck as these are very interesting animals,