Minnow Aeration

I'm not sure Don what you mean but I presume you have a source of 110 v ac and want to step it down to around 12 v using a transformer, then rectify and possibly filter it

Am I guessing right

Been a long time since I did these types of calculations, but just off the top of my head, about 110/14v Ac. Then the rectifier and filter, where you'll lose a little bit. You'll probably have to get it made specifically for your purpose. Go to a transformer manufacturer, and tell them what you need.

Wilsdo is right on, don. Your exact output voltage will depend upon such factors as winding resistance of xformer secondary and choke (if used). And 14 vrms is also a good guess

However you ought to be able to find one on the market, even surplus, for a pittance