Another fish is never a bad thing. :)
13 gallon? That's a strange number, most tanks I've seen come in numbers that end in .5, 5 or 0. That's pretty cool.
10 Gallon Tank:
~Countless Pond Snails~1 Espe's Rasbora~1 Harlequin Rasbora~
5 and 5.5 Gallon Tanks:
Avatar by Fenghuang
Many of my scaly friends from my original tank from 2011 have passed, except for two! I am in the process of re-doing my tank. :)