I developed a 120 roll of T-Max 100, in a small metal tank & reel, with T-Max developer for about 7 minutes. However, I'm having a severe problem with black circles. If I understand correctly they're caused by bubbles stuck on the film during the developer.
There are more bubbles in the centre of the reel, and a lot of bubbles close to the edges of the film. Running my fingers down the edges of the film I can tell it's not smooth/straight where the marks are. If it's of any relevance, I have very hard water in my area.
I used a few drops of wetting agent in the developer as I've heard it helps prevent bubble marks. Perhaps I used too much and caused too much foaming inside the tank? Then again I almost filled the tank with developer so there wasn't much space for foam and to play around in.
I agitated the tank the first 30 seconds and then 5-7 seconds every minute. At times I went a bit "hardrocker" with the agitation (in retrospect I guess this would cause even more bubbles) but then again I made sure to bang and thud it often and well.
So, any ideas what I did wrong?