Red tail shark

[Rxhart]

I obtained some fish from a friend who was moving away.p to restart my 75 gallon tank that had been idle for 10 years. He had a lovely mated pair of angels, a 3 inch red tail shark and another feather fin squeaker catfish. I have A 75 gallon where they are housed now. Large angel is dominant to the red tailshark, but rts is annoying other fish, such as an algae eater, and I know it will get worse. Really would prefer not to have him in this tank, and make it a more peaceful grouping. I am thinking I will have to find someone else to take him for the long run. Other ideas? I have 3 other small nano (15 gal)tanks with peaceful fish in them he could not go into.
This tank presently houses:

2 adult angels
5 orange laser corys
1 algae eater ( harassed)
1 bristlenose pleco
4 zebras
1 squeaker cat

 

[Byron]

This is "normal" behaviour for this species, so no surprise. Be vigilant though, because for reasons we do not understand this fish (RTS) frequently takes a real dislike to upper fish with vertical stripes, so if your angelfish are of that pattern... watch out. For the sake of all fish, the RTS needs to be removed and rehomed. Expecting normal behaviours for a species is wiser than hoping for abnormal behaviours.

Don't know what species the "algae eater" is, but some of these are downright nasty with many other fish.

Many fish do not exhibit their true colours due to poor conditions, as in the tank they came from which certainly was not stocked responsibly and that may mean things will suddenly change. It happens.

 

[Rxhart]

Chinese Algae Eater​

(GYRINOCHEILOS AYMONIERI)

 

[Byron]

Unfortunate, this fish (Gyrinocheilus aymonieri) is notorious for its aggression as it ages. From my profile of the species elsewhere:

Compatibility/Temperament: As it matures this fish becomes aggressive, especially toward slow-swimming flat-bodied fish. Should not be kept with fish that remain close to the substrate such as cichlids or catfish. It has frequently been observed grazing mucus from the flanks of other fish. Best kept as a solitary specimen, or a group of 5-6 but only in very large tanks due to the conspecific aggression. Given its habits and eventual size, this is not a fish recommended for the community aquarium.
Diet: When young this fish will graze some algae from rocks and wood but it requires more basic prepared foods, frozen bloodworms, daphnia, brine shrimp, etc. As it matures it eats even less algae.

 

[Colin_T]

Most algae eating fishes are territorial to some degree. This is because they have a limited supply of food (algae) and they don't want other fish coming in and eating their food. It doesn't matter if the fish is well fed, the instinct to protect its territory and food source will always be there.