I've never combined such fish together so no 1st hand experience (except when the eels were too big to swallow for small TSN growouts). I'd say it's a gamble that may or may not pay off long term. Spiny eels are of course noodle shaped but they are smart, weaselly, and prickly and may earn to stay away from the TSN. True eels seem dull in wits in comparison.