How much tank space for a two spotted blenny?

[EstherGreen]

So I am planning a 5 gallon tank, with macroalgae, soft coral, and some sexy shrimp, and think a central fish might be cool. I checked the lfs and they don't have anything smaller than a two-spot blenny. Can I keep one, or should I look for even smaller fish?

 

[fishywishy]

Should be fine.