50w heater in a 30gal tank?

This is just for tonight, as for some reason my heater has blown after almost a year of use. The light flickers on and off for about 30s after it is plugged in, and then it stops completely. I have a 50w that I used for a hospital tank months ago and I was wondering if this would be able to keep the tank heated just until tomorrow. It is a 1 year old 30gal - probably only filled up to 28gal with 15 fish in (X-ray tetras, Black Phantoms and two kinds of Corydoras).