Can I use a 5 gallon carboy for my starter

I have my first lager under way. I made a 1 gallon starter for it about a week ago and the only thing I had that would work is a 5 gallon carboy. I put it in there sanitized everything and added airlock. I am steeping the grains right now and brought the starter from 50 F room and am warming to room temp. I think there may be mold I noticed small spots on the side of the carboy. They are white. My question is can you use too large of container to make a starter?

The large container shouldn't be a problem. The mold may be though.

Is there any chance the white spots on the side are yeast?

Also the starter smells great...

Can you post a picture? If it smells good than its probably ok.

I should of done that first thing. Instead I shook it to see if they would go away and they did. I think I'm going to use it. After looking at some of the other threads regarding white spots it seems that it was likely yeast colonies.

Sounds like a brilliant way to get a starter going and evenly distribute and mix, I may do this for my next batch. Thanks for the idea!