Zigzag spiny eels stay pretty small (about 5") and should be ok. Make sure you don't have any fish that can eat it (my bichir ate mine ) Also they appreciate being able to bury in sand.
Just make sure that tank is covered. I have a small peacock eel (>4") in my ten-gallon now. If you don't have a hood, I would recommend an Eclipse hood, with built-in filtration.