20g is too small for pictus long term I think, they can hit 4/5 inches in aquaria so I would try and swap them for an other upside down catfish so you have 3 of them then. Just to add a 20g is too small again for the glass catfish that cossie suggested and I also worry that the krib wont accept a gourami and in most cases I would think the gouramis would be too squishy to withstand any kind of attack.
With regard to the krib is it male or female? If you wanted an other krib you could try taking the krib out re arranging the tank introducing the new fish then re introduce the original krib about half an hour later.
Perhaps a good fish for your tank would be the black ruby barb a nice school of 6 would look good I think and are tough enough to act as dithers for the krib.
Wills