I hope I am correct in reading your (Stephen2k3) posts as meaning you have seen this fish but not acquired it yet.
Taking the Congo Tetra (Phenacogrammus interruptus) first since you asked about this species, it must have a group. The fish in the photos is male (whether same one or two), easily identified by the longer dorsal fin and the middle extensions on the caudal (tail) fin. Females do not have such fins, and will be less reflective in colour. It is best to get a fairly even ratio of male/female, say three, four or five of each, though you can have slightly fewer females in larger groups if you prefer. But with a good number and a gender mix you will see some lovely interactions. The tank should be 48 inches/120 cm in length. A 240 liter/60 gallon might work, if you could give us the dimensions (length especially). This fish needs space to swim and the males will do what I term relay races down the tank if they are "happy."
The Bala Shark noticed in the photos is another issue, but I will again assume these photos are not your tank. So i won't get into the issues with this fish.