the fire eel does grow very slow, he was about 7cm when when i bought him. he grew quite slow in the first 3 months till he reached about 20 cm. after that he grew to 45 cm in 4 months. He then stopped growing for some or other reason and in the last year he started growing again. so it looks like they get growth spurts for the first year and then slow down. He also goes through times, a month or two, when he eats virtually nothing and then for the next month he eats like crazy.