Serpae Tetra Fin Nipping

[V3rmilion]

A few weeks ago I bought 6 serpae tetras (red minor tetras) and 3 Amano Shrimp for my 10 gallon (38 L) aquarium. They seem to be fin nipping each other a lot, and they are in a school of 6 so I am not sure why they are doing this. I have 3 fake plants, a moss ball, and a large log decoration in the tank, as well as a heater and black gravel substrate. They are leaving the shrimp alone as far as I know, but they will not stop chasing each other.

Parameters:
pH: 7.5

Nitrate: 0 ppm

Nitrite: 0 ppm

GH: 180 ppm

KH: 80 ppm

Ammonia: (My tester doesn't give me an exact answer, but it is a light yellow-green, which is between the "ideal" and "safe" spots.)

Temperature: 78°F (25.6°C)

I can't upload a photo because the files are too large ‍

 

[Essjay]

It's because they are serpae tetras, one of the nippiest species of tetra. I once had some years ago and within days every fish in the tank had bits missing. They went back to the shop.

Seriously Fish comments that they are "notorious as an aggressive community inhabitant....more pronounced when insufficient numbers are purchased or space is limited" https://www.seriouslyfish.com/species/hyphessobrycon-eques/
This is the problem here. They need to be in a group of at least 8 to 10 and in a tank at least 80 cm/32 inches long x 30 cm/12 inches wide - your 10 gallon tank is probably a lot smaller than this. If you want to keep them, they need to be in a bigger tank with more of them. Or do what I did and return them to the shop.

 

[seangee]

I too was seduced by their looks and bought some. Mine went back too as they were nipping everything in the tank. They really need to be in a group of 10-12 and a bigger tank (ideally at least 3'). Even then they will still be aggressive. I had 12 in a 4' tank and still took them back because they were too aggressive ...

 

[Byron]

I concur with other members here. This species, Hyphessobrycon eques, is notorious for serious fin nipping within the group, but also to other fish in the tank.

The species must have at least 10-12, and this number must be in a 30g tank (with a length of 30 inches (75 cm) minimum. This is the minimum for just this species on its own; with any other fish the tank must be significantly larger, but even then the tankmates need to be very active fish. Sedate fish will be mercilessly nipped to death.