To the video. As mentioned earlier, I know Oliver and have corresponded with him. We are on opposite ends (almost) of Canada so meeting in person is not easy and hasn't yet occurred [he travelled to Vancouver some years ago to speak at a meeting I could not sadly attend due to a round of cancer treatments, agh!]. I recommend this video heartily as reliable information/data on these fish and their habitats. There are some inferences we can draw however, and they are important for a correct understanding.
First, notice the environmental factors present in all the habitats of this fish shown. 1. Always a shoal (group) of dozens if not hundreds, and tight together (except the one shot where the two were "hiding" for good reason). That is condition #1 for peace with this species, and it is where most aquarists (beginning anyway) fail with this fish...too many in too small a space and the fish rebels. [Scientific studies have led us to the conclusion that a species like the present one should have 12-15 minimum, and in their own 30-gallon (30-inch/75cm length) tank; other species, except probably for substrate fish, requires larger tanks than this minimum. 2. Always shoals of other, generally larger, fish nearby--this too has quite an influence on fish behaviour, as studies have proven. This we can only replicate in very large tanks of course, but in the habitat it is a signifant factor for the fish. 3. And, the water movement--this video is not indicative of how these fish usually spend about half their year, in flooded forest when they spawn and being in calmer water are not only further away from the "predators" but more relaxed to pursue natural tendencies; and they are more concerned with feeding and spawning in the richness of the flooded forest rather than just surviving. And most of us provide water movement closer to this that a torrent, for good reason...but it
does impact fish response in several ways including behaviour.
Second, temperature. Darker colouration in fish can mean stress from cooler temperatures, biological fact. I'm not saying it is the issue here, just note it as a fact. Paler colour often comes from higher than "optimal" temp, as others (
@Colin_T) noted. The low temp (below high 60'sF/20C) of southern watercourse in SA is correct, obviously, but one has to consider just what fish species live there. And, I previously detailed the considerably large geographic area this "species" inhabits, and Oliver referenced that in the video. There is also the confused phylogenic history of this "species," which again Oliver referenced. Evolution has been active here, and that must be understood as the backdrop to what we find today.
I can draw a sort of parallel with another very commonly-seen species, the Pristella Tetra (
Pristella maxillaris). This latter fish also occurs over a wide geographic area [areas of the basins of the Amazon and Orinoco systems, and coastal river drainages of the Guianas; and in some very diverse water parameters--it has a range of soft to slightly hard (hardness up to 30/35 dGH), acidic to basic (pH up to 8.0) water, temperature 24-28C/74-82F. But the fish that live in each of these diverse habitats have evolved over thousands of years to do so; they do not migrate from one to another as they are geographically prevented from doing this. You cannot take a wild fish from "x" and place it in "y" with good results. This is no less true for
H. eques or whatever species "they" may end up being, and I trust we all recognize that this is important; nothing out of context in biology as in research.
