That sounds lovely, I think it would be OK to have pencilfish as well as tetras, as the pencilfish tend to keep near the top. I will let someone else advise as to numbers of each.
I see kind of a problem here: Dicrossus are as softwater and low pH as it gets just for holding conditions. They don't do too well in tapwater (GH over 5-7 and pH significantly over 7 is not advisable). I keep a single male in a 100 liter tank (80x35x40) with tetras and pencilfish, water parameters: GH/KH below detection, TDS 30-50, pH 5-5.5. I strongly recommend these parameters for growout and longterm keeping.
Even a higher chance of ending up with only males and a high chance they become aggressive earlier. As juveniles a bigger group makes them much more outgoing. Your call. I would go with 5 still.
Thing is, you will basically use the tank as a growout for the first months. Means: Lots of food, lots of waterchanges. So for the start stick to pencils. They have extremely low bioload and won't eat all the food before it reaches the Dicrossus at the bottom. Once the Dicrossus are sexed and sorted you can add tetras. That's how I went through with it.
Neat fish. I tried to have a friend put some in his pockets when he returned from Canada….$18a fish was a pretty fair price. I’d expect them to be like A diplotaenia, and unlike pretty much every other Apistogramma. Provide lots of sand, little cover above the substrate, and lots of cover within the substrate
