The Red Line Lizard Tetras are fascinating, medium sized pelagic fish that grow up to 9cm long. They are slow moving and seem to swim against the current in slow motion. Their slender bodies seem to wiggle as they swim against the water current. Their body movement remind me of the way a Green Iguana swings its body from side to side as it crawls up a tree. If you are very patient and take your time to approach them slowly, they will let you get quite close to them. These fish have been exported and sometimes sold in the hobby as Iguanodectes geisleri but they are definitely not I. geisleri because they have more than 25 anal fin rays. They also differ from Iguanodectes adujai by having a body height which is five times the standard longitude.
Red Line Lizard Tetras have a pink to red colored lateral stripe starting at the end of the operculum, thinning and ending below the adipose fin. They also have two red spots in the caudal peduncle over a large black spot both of which extend half way into the caudal fin. Their pectoral, dorsal, pelvic, anal and caudal have a strong yellow color that fades out towards the ends of the fins. Their body colors seems to vary or change a lot, from a light beige to a bright green. The color change seems too strong to be caused by the reflection of the colors from its surrounding habitat. Probably the color difference are due to gender, mood, how the light hits them, or probably just varies from specimen to specimen. The red spots on its caudal peduncle sometimes makes it resemble a traffic light. The red line they have right above their mouth makes them look as if it had red lipstick. Now this is what I call a cool aquarium fish.
It is possible to divide a stream into many different habitats; these habitats differ mainly in current speed, substrate, depth, and plant growth or accumulation of driftwood, just to name a few. These smaller habitats, sections or systems are inhabited by permanent or transitory tenants. Red Line Lizard Tetras “hang around” three types of sections of the stream, all of them less than a meter deep. Their favorite section of the stream is the heavily planted river banks. These are less than 40cm deep with lots of aquatic plants and a medium fast current. They specifically like to swim in narrow corridors between the aquatic plants. I let go of a leaf underwater and it took the leaf around 5 or 6 seconds to travel 1 meter downstream. So, in the square meter in front of me where the Red Line Lizard Tetras were swimming they received an average water change of 72L per second. This is where their body color seemed the greenest.
The second preferred habitat are the river depositional zones. These lentic habitats have a very slow water current. It is one of those spots in the river where all the dead stuff winds up rotting. The aquascape is a monochrome of ocher tones. Dead leaves, fallen branches and all the silt deposit here. It all resembles a phantasmagoric, surrealist Salvador Dali painting. Probably this is a place where they take a break from the strong water current. It definitely was not a transitional zone, because they stayed there for long periods of time. In this spot their green body color was not so strong but still striking. With their green body, red stripes and yellow tones they resemble live moving ornaments between dead Christmas trees.
The third habitat in my opinion is one of the dullest sections in the river. This is the streams narrow deep straightaway or runs. The fast oxygenated water current seem to attract all the fast swimming tetras in the river. Everything here is a monochrome beige color but is a tetra paradise. The thin fallen tree branches vibrate as fast water pass by them. Here the Red Line Lizard Tetras are always hiding behind these branches which seem to shelter them and give them a break from the strong direct current. For some reason, here they seemed to lose most of their green coloration and turned almost beige. It seemed to me that I was looking at a different species but all the traits were the same except the lack of green coloration.
The Red Line Lizard Tetras are as peaceful as a fish gets and opposed to many other tetras of the same size it seems not to swim around too much and do not like open waters. It spends its day behind branches or behind aquatic plants where it seeks shelter from the direct water current. They feed on the organic material that is dragged by the water current and happens to come their way. I have also seen them picking on the periphyton and algae stuck or growing off the natural decor including aquatic plants leafs and fallen branches. They are one of those tetras that do not swim around much, they actually keep the same location for a long period of time in the river, just fighting the current without going anywhere. A good example would be a fly in a glass window, they have the effort but go nowhere. Once in a while they spot a succulent piece of algae growing on a rotting fallen tree branch, they take a bite and go back to the exact position they had when they started. So you can say they also resemble an Iguana because they feed on the green that grows on tree branches.