The Prognathodes genus is a remarkable group of fish. They are generally reef safe, have striking proportions, handle treatments well (e.g. copper), and have extremely curious personalities. Of them all, the deepwater French Butterflyfish (Prognathodes guyanensis) is arguably the most coveted in the aquarium trade. As I outlined in the P. guyanensis x P. aya hybrid […]
The Prognathodes genus is a remarkable group of fish. They are generally reef safe, have striking proportions, handle treatments well (e.g. copper), and have extremely curious personalities. Of them all, the deepwater French Butterflyfish (Prognathodes guyanensis) is arguably the most coveted in the aquarium trade. As I outlined in the P. guyanensis x P. aya hybrid piece, both the French and Banks butterfly have been recently collected in parts of Florida–this is no different for the fish shown here.
P. guyanensis is very rarely available. If they do make their way into the trade, they are typically sent to Japan and sold for as much as $2,500. (LiveAquaria recently added a Guyanensis to their Diver’s Den section, shown below, which is still available for $1,300. If all goes according to plan the hybrid will also be available for purchase soon–but I cannot imagine the price for this fish!)
A good friend of mine purchased one of the first P. guyanensis that were collected. It arrived to him physically looking fine, but refused to eat. With an upcoming trip, he did not want to leave this rare fish in the hands of his normal tank sitter–so I got a very comical phone call leaving me with the chore of cracking this butterfly and enticing it to eat–a task that proved to be quite difficult.
The 2″ thick styrofoam box the fish arrived in was destroyed with one corner fully crushed. Thankfully the fish was packed in a large bag with oxygen and ample packing peanuts for protection. FedEx was kind enough to yell at me that the box was leaking water all over the truck before delivery…
The fish was physically unharmed, but the bumpy ride could not have helped. It took four weeks in captivity for this Mariposo to even take interest in feather dusters. I was amazed at the size of the specimen. This fish was nearly 5″ from nose to tail with the largest dorsal spines I have seen on Chaetodont.
After trying a variety of foods including live blackworms, live brine, clams on the halfshell, live rock, coral and feather dusters it did not take long to see that the fish was still under some type of stress. Large water changes were performed to keep 0 nitrates. Initial water temperature was kept at 72F. This was slowly dropped to 68F and the fish became noticeably more comfortable, but still no eating. P. guyanensis often live at depths of 500ft, as such I sided on cooler and darker.
At such depths, sunlight is filtered providing a deep blue color temperature that pales in comparison to what is found on shallow water SPS reefs. This particular fish constantly hid when the aquarium was illuminated by an 26w 8,000K spiral CFL. It would only venture away from its cave when the lights went off–noting this I kept the lights off for three days. The following day (a total of 25 days under my care) the fish began eating grazing on copepods and feather dusters on the liverock. The day after I had the fish eating prepared foods, using a frozen paste method to train the fish to eat out of the water column. A week later the fish was accepting pellets.
I continued to experiment with the fish’s apparent photosensitivity by feeding with the lights off and then turning the lights on while food remained in the aquarium–as soon as the switch was flipped, the Guyanensis would dart to cover and ignore the food. Turn the lights back off and feeding would resume.
The fish was slowly acclimating to brighter light using a 9w Blue LED spotlight to illuminate the aquarium, hence an increase in the blue and purple tones reflecting off the fish’s silver body in these photos. This French Butterfly has since been acclimated to full reef lighting and a warmer temp of 72F. A couple weeks ago the fish as shipped back to my friend–who reports it is healthy and eating well. For Chaetodontidae fans and rare fish enthusiasts, it doesn’t get much better than Prognathodes guyanensis.