30 inches long. I heard they can be fin nippy, but will that calm down if I keep enough?
This species, Hyphessobrycon eques (Red Minor Tetra, Serpae Tetra, who knows how many other common names), has very specific requirements, which incidentally mirror exactly those of the Tiger Barb. First, they need a group of 10-12 (or more), and this means a 29g minimum tank. Just for this species. Substrate fish like cories can usually work, but no other upper level species unless the tank is considerably larger than this.
The reason for this number and the tank is that it usually keeps them relatively peaceful. Smaller groups will cause fin nipping among them...the white edge to their fins is due to fin nipping. With 10-12 or more, this is usually not too much of a problem, but individual fish within a species may not follow the norm and there is no guarantee.
In larger tanks, other fish species can be considered with these. But, never any slow or sedate fish, and never any with long or flowing fins; such fish are like waving a red flag in front of a bull.
It is unfortunate that two of the most commonly seen fish, and two of the most attractive, have such terrible behaviourial issues, making them unsuited to many tanks, especially beginners' and smaller than 30g.