So are we saying get a bigger tank? Yes. Will the do fine in the 20g? Yes. But if you want them to reach there full potential you should look at getting a bigger tank in three to four months your going to have a problem or you will be in my shoes. I have to do 25% water changes a day after feeding just because the waste and how messy they eat. I think you will be fine with the 20g for another month but after that your asking for trouble. IMO....