Article © Richard Smith, uploaded February 29, 2012.
This month's featured species is brought to us by CotM debutant Richard Smith. A serious catfish connoisseur, Richard introduces a less than commonly kept species he is keeping successfully as evidenced by the pictures that accompany this article.
I think we all have certain fish that grab us and don't let go - our "must have" fish. Unfortunately, at least for my wallet, I have a few such fish and Leptodoras juruensis is one that recently "caught" me. At the time of writing, the genus Leptodoras has eleven members, which is more than any other genus in the doradidae. Despite of this, Leptodoras are rarely seen for sale. As a result, few aquarists get a chance to try them. This leaves me wondering why?
Well to start with, there is not a lot of information available on them. If you are new to the species, it will be hard to get advice and guidance on how to keep them. Secondly, L. juruensis hails from the Juruá River, a southern affluent river of the Amazon. From what I understand, they live in deep white-water river channels. I would imagine that this makes it difficult to find and catch them. Finally, they have a reputation for being "difficult" fish because of their complicated diet, which consists of plankton and detritus, as well as chironomid larvae and other food. All these issues combined may be why they are rarely seen in aquaria.
All Leptodoras have elongated bodies, but L. jurensis takes it slightly further. They are more slender in build and appear even more "stretched". They are recorded at 29cm when adult. Colour is not remarkable and on most specimens below the line of scutes they are a typical fish-white colour. Above this line they are a muted purple-grey which extends to the head. Finally, the gills can have a pinkish tinge. The dorsal fin is quite different to any other Leptodoras, the first spine being greatly extended. The paired fins and the base of the dorsal are black on adult fish — very smart!
It seems their mouth is specially adapted for hoovering food in sand or silt. However if you consider certain other catfish with specially adapted mouthparts, like some loricariinae, they also use their lips to hold and protect their eggs. I wonder if Leptodoras do the same? Why else would they have such an elaborate mouth?
I first saw a photograph of this fish back in 2010 at Steve Grant's online catfish album. “WOW”, I thought, what a very exotic, stretch-limo of a fish, and decided there and then I wanted it. Next thing I did was to contact Neil Woodward at Pier Aquatics (UK) about them. It turned out Neil had been on the look out for quite some time and he had found a possible supplier. You can just imagine my big cheesy grin when I heard this! I made some enquiries about their husbandry requirements but little was known and a lot of it was based on assumption. At one point I contacted Doradid expert, Mark Sabaj and even he was not sure of their temperature requirements. Neil at Pier didn't know the answer either.
At the outset, I was confronted with there being little information stating the ideal aquarium conditions for L. juruensis. The requirements of these fish was, to some extent, guesswork. They certainly are not from blackwater habitats; I thought it best to play mainly neutral. To begin with, I maintain them at 80-82°F and they appeared comfortable with that, although I suspect the deep channels in the Juruá River might be cooler. I keep the tank pH just above 6.5 and TDS is around 120-150. I perform a 40-50% cool water change every week, same with all my aquaria. The 5' (150cm) tank they live in is part of a 750 litre system. Two tanks overflow into it and all the water is filtered in a sump. In addition a fluval external filter is on the tank creating extra flow. During mid 2011, I added an air ring to the fish room and every tank now has a large sponge filter. This was fitted to increase aeration and as insurance in case any other filter failed if I was away. My L. juruensis, together with their pal, L. linnelli, are kept together in a dimly lit tank; there is plenty of swimming room on the sandy substrate. L. linnelli apparently prefer cooler water, but so far my specimen is doing nicely.
As is common practice in order to avoid fowling the water, exporters stop feeding fish before their journey across the world to retailers. However, if it's true that L. juruensis are specialist feeders, then it is unlikely they will have eaten anything since being caught and this will make it more difficult than with other species to get them to start feeding again — this is the first real battle.
At Pier Aquatics, after trying various foods, they observed some of the fish eating chopped frozen tubifex cubes. Well that's a good start, but long term they really needed something more substantial and nutritious. Other off-the-shelf frozen live foods would appear to be eaten but then were ejected via the gills every time. Once home, at first I relied on the experience I had of another "difficult" long and slender fish — the glass knife. What I observed was that dried foods were totally rejected and typical live and frozen live foods just didn't seem to provide bulk in the diet, they also pass through the gut quickly. On these foods alone a glass knife will slowly get weaker and eventually die.
The "super food" that was the solution for the knive fish and also for L. juruensis is no secret -it's worms! To be precise, very finely chopped frozen dendrobena (compost worms). These are available, in the UK at least, from fishing tackle shops. I buy a half-kilo at a time, wash, drain, freeze, and cut a chunk with a sharp knife and chop. For these fish you keep chopping almost to a pulp, if you do it quickly its not messy because it's frozen. I could see the Leptodoras were eating the food, it was the breakthrough I needed and I stepped-up the feeding to three and even five times a day when possible.
The second important food is shrimp paste. I've heard of lots of different versions and ingredients. My current recipe is raw prawn, cooked mussel, spinach, peas, garlic - all whizzed-up individually in a blender to a pulp, mixed and then frozen. These two foods form the base of their diet. They both provide bulk and are nutritious. I noticed my Leptodoras were growing and their bodies were thickening. Now they were eating well I also offered them enriched brine shrimp and tubifex again. This was happily consumed without any rejection, although in a fast current the tubifex goes everywhere! More recently, I've observed them showing interest in dried foods, notably brine shrimp pellets and veggie-based pellets, when the pellets are soft the Leptodoras like to suck on them and their stomachs looked full - this was another breakthrough. So it's fair to say that keeping these fish gets easier. Now they are eating pellets I only have to feed prepared foods two or three times a week.
When you add up their capture, transport, not feeding and the overall stress, infection is a real risk and their ability to fight it is reduced. All catfish are scaleless and are generally more sensitive to medicines. However using salt, high temperatures and strong oxygenation one can fight white spot infections. Getting my L. juruensis to their healthy and happy state has taken a while. It's been something of a costly exercise because I lost a few of these fish to white spot early on, which was sickening. It had been years since I lost any fish to white spot, let alone a beauty like this. Thankfully, my persistence and stubborn streak eventually paid off and I now have two healthy specimens plus a robust L. linnelli to keep them company.
Finally, a real bonus with my Leptodoras is that they are nearly always at the front of the tank. There they enjoy the current from the filter outflow. They are more visible and less shy than any Corydoras I have ever kept, which is surprising for a supposedly deep channel river fish. Both species are currently about half adult size, so their behaviour may yet change.
Copyright information for the images used in this article can be found on the species' full Cat-eLog page.
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