I think M. electricus is the most common and available imported species. It is reported to grow 4 feet in habitat. Mine grew to 1 foot in seven years. It went from a 10 gal to a 55 to a 125 and died right before I wanted to move him to the 180 gal. Here's my 1st Question: Do you think it would have grown larger over time and with the progressive tank upgrades? Does anyone have any experience keeping larger or older specimens? In what size tank were they kept? Was the cause of death the weird bloat that appears to be from electric organ discharge failure when kept in tanks?
Also available is the less frequently available M. microstoma which reportedly grows to less than 2 feet in habitat. Looks to me they have the more pointed mouth with larger lips and a dorsal fin that is more pronounced and are more grayish than brownish. Btw, upon closer inspections of Rudy's older pics, his looks to me like microstoma. Here's my 2nd Question: Why do the large 3 footers that I see online ALL look like M. microstoma?
I'm beginning to think that the published information is inaccurate, or just mixed up. I think that the M. electrics grows to 21" in habitat and grows to around 12" in aquaculture and the M. microstoma, the "dwarf" grows to 48" in habitat and around 36" in aquaculture. These are my observations. I did see a subspecies page online with over a dozen photographed specimens, some of which were preserved subspecies. Most of the subspecies with discernible featured were reported to be rarely available and the others looked so similar or so dried up, it was hard to make sense of sub specific differences. Go figure!
Any input would be much appreciated.