if he doesnt get a constant supply of bloodworms, fire and tt eels naturally i find tend to go towardfs raw shrimp and meaty smelly foods like mince beef heart, shrimp and fish fillets - all raw. never cooked.
pellets is good, they get a massive concentration of protein and vits and grow rapidly but i have only ever had one fire eel that actually hard out fed on pellets, i mean ate pellets like it was prawns.
the growth is faster, girth is better BUT as far as pellet growth vs meaty - i did not notice a drastic difference as i did other fish so i would say, might as well just feed prawn (my next eels i will not bother with pellets)
when big enough (40 cms plus) you can stuff pellets into shrimp to boost its growth.
basically, dont let the eel starve, when teh body is tapering thinner than the skul thickness, its starting to get stunted and chronic malnutrition.
Also remember - most , a large majority of tt and fire eels will NEVER reach full size potential due to multiple factors.
1) not enough room
2) not enough food
3)quarantine stunting
4) lfs age unknown
actually, this applies to most fish that dont move too rapidly in our local shops.
basically, if a fire eel stays in a shop for 6 months whcih happens regularly, and it only grows 2 cm in 6 months - whcih also happens, then you know this is more likely gonna be stunted.
Bird barn in auckland had a massive fire eel, certainly not stunted to get to that size
i got one from hollywood that ate massivore and hikari arowna sticks - that was not stunted, i got a 40cm tt eel from I FORGET WHERE lol and not it is literally 73/74cm+.... thats luck IMO.
This i found is similar to clown loaches. Once i had more than 80 clown loaches - HUGE SCHOOL.
only about 15 to 20 grew fast, even though all of them ate lots and always fed well, water is perfect.
Then after a few more months, the 15 to 20 grew rapidly and kept growing while everything else grew very slowly.
This could be hormonal, genetics or stunting in quarantine or all of the above perhaps, who knows.