Ralph Davis uses bleach too, check out his youtube videos. I use 1.3 groups for communal breeding in those cement tubs. I only use this setup sparingly since a lot of groups don't mesh.

I prefer to separate pregnant moms. I use the cement tubs as their breeding tubs. I place three males and up ten females in a tub. I will probably get flamed for this but hear me out. The males have to grow up together. If you throw in three adult males that don't know each other they may kill each other. I like this method because as soon as a female rat is receptive one of the three males will knock her up. If you use one male I feel you are more likely to run into problems. Female rats are funny. They will not breed if they don't like a certain male. Just watch Ralph Davis' videos . He rotates his females through the males tubs every week for this very reason. If you use three males no rotation is necessary and you need less tubs for breeding. For the females I place them in some old school Bush tubs that are about 15 inches by 15 inches. I usually put one or two females in each tub to give birth and wean. Sometimes I place three females in a tub if I start to run out of space or if the weather is really cold. I prefer to place females together that came from the same breeding tub. I feel they are more accustomed to one another and less likely to fight over babies.

David