I'll respond to your stocking questions, but first a quick comment on the cycling...what are you adding for ammonia? Cycling times vary as so many factors are involved, but it can be from 2 to 8 weeks usually. Of course, using live plants, you can forget cycling. I'll explain if asked.
To the stocking. I would certainly not add Red Minor Tetra. First, a 20g is really insufficient space as this species is best in a larger group (12+) and a 30g for just this species is minimum. Second, never add this species with sedate fish like gourami. While there are always exceptions, the general tendency of this species (Red Minor Tetra, which is another name for Serpae Tetra, scientifically Hyphessobrycon eques) is to be rather feisty. Kept in smaller groups they usually fin nip each other. But when sedate fish are present, they are often--nearly always--targeted.
There are some lovely suitable tetra which are near-identical in appearance, such as the Rosy Tetra (H. rosaceus) or Robert's Tetra (H. bentosi). However, you might want to re-think things. A 20g long is not much space. If you want more fish for added interest, look to the "dwarf" species in the characins and rasbora, pecilfish, hatchetfish. The gourami or Rainbows might be problems here, as all these are not necessarily suitable. What are your water parameters, meaning GH (general hardness) and pH? These can be important especially if we are considering wild-caught fish. You can ascertain the GH and pH from the water supplier, probably on their website.
Byron.
