Both are to large for that tank, the pike characin gets to 13" and the texas gets to 12". Your tank is around 6 gallons, this would be barely enough for a pair of black banded sunnies. The max adult length of a single, relatively inactive predator for that tank would be 6", and that is pushing it. You will also need to avoid those fish that are chasers and darting types, that is basically all of the long, thin ones like the boulengerellas