The 40L translates to a 10 gallon tank and the foot print (horizontal swimming space) is a little small for active fish such as danios; this include glofish.
Suitable alternatives include White Cloud Mountain minnows, harlequin rasboras, tetras (the smaller varieties), and guppies. I not sure how much of each you should add. Hopefully others will chime in with their input.
The aqua advisor site does a nice job providing feedback on your tank setup when you supply the tank dimensions, filters, types and numbers of fish you plan to add.