Breeding ASF rats proper ratios for a 20 gal and 30 gal tank????

Hey i was wondering i got 20 gal and 30 gal tanks ready to go for some ASF rats wondering though what is a good ratio for these size tanks for breeding purposes?

I was thinking:
1.6 for the 20 gal and maybe 1.8 for the 30 gal

You guys think that's too much for the tank size ?

Right now i got a whole bunch (16+) in the 20 gal and seem like enough room to me for them.... open for suggestions from the pros as i would like to have them comfortable and breeding