dwarf puffers are really aggressive plus colombian shark catfish get really large and will eventually need salt water. plus the puffers are only 1 or 2 inches the shark gets 11inches
The shark will get to a minimum of a foot long. Probably too big for a 30 gallon tank. Also, when adult, the shark will require brackish water, where the puffer doesn't like brackish water. Puffers also tend to be very agressive, but in this case the dwarf puffer may look like food to a much larger shark=