I have an extremely aggressive Koi Angelfish about 5 months ...

I have an extremely aggressive Koi Angelfish about 5 months old terrorizing the other three Angels in my 75 gallon planted tank. I would like to get him a new home but fear his new home may not be as nice as what he is used to, so I am worried about finding him another home. Do you think an Angelfish would care about a lesser quality or smaller new home, or losing his tank mates? Do you think I am exhibiting a classic example of anthropomorphism worrying about this fish's well being should I have to part with him?

JohnArhtur will be on in the morning, and he is very experienced with Angelfish, so he will be of WAYYY more help than I would ever be!

I wish you luck though!

Thanks for visiting.

Anthropomorphism is difficult for our species to avoid, especially when the behaviors of creatures like angelfish are so similar to our own. If you had the angelfish for five months, chances are he's a couple months older and has reached puberty, which makes him act like a school yard bully. If he's just chasing the other fish, make sure they have plenty of hiding places or move him like you suggested. If he confronts another angelfish and they are mostly twitching and lip locking, it is, of course, a mating ritual, which sometimes gets pretty violent. A spawning pair needs their own aquarium; the 25 gallon tall works well.

It usually takes an angelfish about a year before their hormones take over, so maybe the other angelfish have not yet matured. Females can also be aggressive, but mostly that happens when they have eggs. The aggressive Koi may settle down once he establishes his territory, which will be close to half the tank. If you have only males, the aggressive one could kill all the others. If you want to read more about gender determination in angelfish, use our search function at the top of the page.

Angelfish, buy the way, will drive you crazy and will have you buying more aquariums. I love 'em.

Hi there again,

My fish were all obtained from the same breeder in Oct. 09. The fish had dime to penny sized bodies.

Oh and to top it off, I was given this fish. I hadn't asked for it or bought it. When I had purchased three other Angelfish from the breeder, he threw in two extra Kio Angels at no charge.

(One of those Koi sadly died three months ago, when I moved him to another aquarium, because of the bully. I am not sure what happened, but both fish that were moved to that aquarium died). It has since been torn down and totally done with new substrate and plants.

Now, one Angel has laid eggs and she is accompanied by another smaller Angel, they began pairing off two months ago.

The larger of the two who paired off, laid eggs while I was at work (apparent by her extended omnipositor tube). I do not know if other paired Angel fertilized the eggs or not, for I once read that if no male is around a female will act like a male in some breeding situations.

The third of the Angels is passive and bothers no one; staying out of the way.

The large Koi Angel chases everyone, including the Cardinal Tetras and Cory cats; but mostly the egg laying female, who has the most shredded/damaged fins.

I really couldn't afford one more fish aquarium and no pet shops in town suited me, so I put this fish on Aqua bid to no avail. When I asked people I knew, if they wanted him, no one did; although I did get many responses like, "No but I'll take him on a cracker�..... You get the idea.

I also put him on Craigslist, with one person inquiring, but that person never wrote back after I asked him some questions about his knowledge of Angelfish.

So back to the original problem, if I put this fish by himself/herself will he/she be lonely?

Sorry about the lengthy post, but no one else would understand this dilemma and it really is a problem to me.

It probably will not bother the angelfish to put him alone for a while. In fact, that's one treatment for a bully. Change a little bit of decor in the original aquarium, then return him after a couple of weeks or more. By that time, other angelfish will have established territories, and the bully will be somewhat disoriented. It also works on pairs where one fish becomes too aggressive with his mate. When introducing any fish to a new aquarium, you may want to use the drip acclimation method to reduce shock.

If the eggs are infertile, they will grow a white fungus in a couple of days. If even one starts to wiggle, they're fertile. Angelfish eggs are very delicate, so any number of things can kill them.

Angelfish are very effective predators, and they have been known to have neon and cardinal tetras for lunch. If you can't sell the angelfish and still don't want to isolate him, aquarium shops will sometimes take them. Do you live anywhere near Phoenix, and do you have a shipping box? I may be interested if he's a really nice angelfish and if shipping is cheap.

Let me show you his pictures. He is pretty I think. How do I post a pic.

P.S. I live in Florida

Your answers are very informative, thank you. I posted some pictures of the mean Koi under "photo albums, general".

From the pictures, it does look like a male angelfish. He has some nice fins and colors.

He's a very nice looking fish!

If you can't really set up another aquarium... In the past, when I had aggresion issues... I used a large bucket... and an airstone, perhaps a small heater (depending on the length of the stay) I would use water out of the original tank, (during a water change is a great time to do this) and fill the bucket. Put the problem fish in the bucket for a couple of hours, as JohnArthur said, moving the decor around some... and then reintroduce him.

I understand getting attached to them. This is worth a try, sometimes it works... other times... it doesn't.

Good Luck in your dilema with your fish...

Hi again.\

I love this Aquarium Club and am happy to be a member. Hopefully one day I too will be able to help someone with advice. Thank you everyone for all your advice.

The latest on this mean Koi. I have him on Ebay and on Craigslist, I really don't want him. I did isolate him to 30 gallon aquarium and had problems with the mated pair in 75 gallon. They began attacking the passive Angel horribly; would not relent.

I then moved passive Angel to 30 and put Koi back into 75 with mated pair. This is the presnt ideal solution. The passive Angel seems to be fine in the isolated 30 gallon and the mated pair and Koi are not as aggressive to each other as they were when the passive Angel was present, even though they still fight it seems the mated pair hold their own fairly well.

Putting the Koi into isolation did work at first, but I did not rearrage aquarium decor, but may have to eventually. When he was put back into 75 gallon, the Koi did seem disoriented at first, but soon he was back to old behavior; which leads me to believe if I had rearranged things it may have worked. But for now the terror he reigns is not as bad as it was with passive Angel in the aquarium. Strange. I cannot figure out what sexes I have here but the problem is not quite as upsetting as it was.

Anyway live in south Florida who would like a Koi? You can have him.

I will post profile soon too. Thanks again everyone.