i did not know about the angelfish numbers. i thought 2 was fine. we use to have 2 and they were very calm although 1 was never really good and died after 4 months.
is one angelfish okay?
First, let me say that through scientific study of a species we (aquarists/hobbyists/scientists) have learned what a fish species requires to be in good health and, for lack of a better word, happy. There are always fish of a species that behave outside the norm, for various reasons. Sometimes the reason is obvious, such as tank size, numbers of the species for a shoaling/schooling species, certain other fish species in the tank, the decor, etc. And, sometimes an individual fish will be contrary to the norm, for reasons unknown. All animals, and people, are like this. But having learned as much as we can about "x" species, we try to provide what we know they are comfortable with, in terms of the afore-mentioned factors.
Angelfish is a shoaling species. Its shoaling needs are somewhat different from the majority of shoaling species such as all characins (tetras, hatchetfishes, pencilfishes), cyprinids (rasvboras, loaches, barbs, danios), atherinids (rainbowfish), some catfish (cories for example). With angelfish, the shoal is about 30 fish that remain together around sticks, logs, plants in the habitat. They develop an hierarchy. A male will select a female and spawn. In the habitat this poses no problems, because the other angelfish in this shoal can move sufficient distance to not pose a threat. In the aquarium, this does not play out the same, except in huge tanks. I recall watching this behaviour very clearly at the Vancouver Aquarium a few years ago. The group of around 15 angelfish (
Pterophyllum scalare) were in a tank that was some 8 feet in height by 6 or 7 feet in width, and 3 or 4 feet depth (front to back). The angelfish were always in their shoal around a set of branches that extended full height of the tank. There was a group of black ghost knife fish above them (these two species are often found together in the habitats). The fish within the shoal nudged each other, as they lived according to their hierarchy. I have seen videos of similar situations, I will post one below; there are I think 14 angelfish in this tank, and they are playing out their hierarch just as they do in the habitat. There are enough of them, and sufficient space, that this works. But this is the ideal angelfish setup, though the video owner does comment that a larger tank is necessary and in the works. But from all we know about this species, this is how to keep them.
I never advise a single angelfish because I don't think it is fair or kind to force the fish into a totally unnatural environment, denying it something it expects. And this expectation is programmed into the genetics for the species, as for all species. They are requirements, and the individual fish expect them.
When you get to two, or three, or four angelfish, it is not enough to ensure the needs of the fish are being met. And if one of these should happen to be male, look out. Males will expect their territory, and that means space. Females may or may not decide to live together in harmony. But what we do know is that it is unnatural. And it is likely to set up a situation that in time if not immediately will be problematic.
