tank mate for a lionfish

[TheMikey]

Ideally a fish big enough that it can't fit in the Lion's mouth. The problem with that, though, is that you're running in a 30g tank and - because lionfish are really messy eaters - your bioload is going to be huge. I hope you've got a powerful skimmer. Also, if you want to keep your lionfish happy you're going to need to upgrade your tank size.