I'm fairly new to the hobby and I decided to start out big. I have a 720 liter tank where I initially bought 4 juvenile oscars. Two black ones, one grey and one white, the white one being slightly bigger than the others but all around maybe 5 cm in length. One of the black ones and the grey one grew alot more than the other two, in a month they were about double the size of the other two and the white one was now the smallest.
This is when the problems started, the big grey one got more and more agressive, especially towards the small black one. When the small black one started to constantly hide under a root (except at feedings, but there were never agressions at feedings anyway) the grey one instead went for the big black one. It started with nipping and ocassional chasing but grew worse over time. One day my boyfriend caught the grey one having cornernered the big black one and was really going at him.
Now we're not sure if it was all from the attack or if the big black one somehow got stuck somewhere but he had really bad like chafing on both of his sides. At this point he was just laying on the bottom of the tank so we took him out and put him in a tiny 30 liter cube (only thing we had) for him to heal. Over the next few days he didn't eat and the scales on his sides peeled off in chunks and you could see the flesh. We really thought he would die.
We kept a towel over the tank constantly so he wouldn't be sos stressed and after about a week he was still not eating but he was no longer just laying on the bottom, if we peeked we could see that he was moving around in there.
We figured the tiny tank must be depressive for a fish that was now almost 10 cm long so we decided to move him back to the big tank and at the same time take out the agressor (grey one) and put him in the small one for now. When we did this the big black one instantly perked up and swam around some, he ate food the next morning and healed amazingly after that, now almost a month later he is completely restored.
The big grey one we took back to the store a few days later. I actually called them beforehand since it was a bit of a travel for us and the guy there was very surprised at the agression. When we talked more back in the store he still said it was uncommon but he did notice that when we put big grey in their tank in the store he wasn't hiding at all even though he was new and kind of small compared to some of the fish in there. The owner had a theory that maybe we had too few fish for the size of the tank, he said when there are only three other fish it makes it easy for an agressor to have "full control".
We left there with two big (almost 15 cm) red shoulder severums and a pleco. Adding the new fish to our tank worked nice, everyone got along fine from the start.
Now after a few weeks the big black oscar is starting to get agressive towards the small black one and the small black one is yet again back to his corner. He never bothers the severums and I'm starting to think this is about size and he bullies the other oscars beause they are smaller. The white one always had it easier, she isn't bothered nearly as much and when she does gets chased ocasionally she just brushes it off. We had a theory that she's a female and the others are male and maybe that's why but we don't know.
How can we solve this? We feel bad for the small black one that mostly hides but we don't want to get rid of yet another big, beautiful fish. Would adding a couple more fish maybe help? Do we have space for it? (we would want one or two more anyway). And also what could cause the growth issues with the other two oscars? They do eat food at every feeding but they just won't grow. The white one also swims weirdly. She's like a bobber, her head almost always to the surface and she almost swims vertically. At first I thought it might be swim bladder but I have seen her "swim straight" so it's not impossible, she also has no issue actually acending or descending so the bouyancy doesn't seem impaired, it's just the constant weird angle.
This is when the problems started, the big grey one got more and more agressive, especially towards the small black one. When the small black one started to constantly hide under a root (except at feedings, but there were never agressions at feedings anyway) the grey one instead went for the big black one. It started with nipping and ocassional chasing but grew worse over time. One day my boyfriend caught the grey one having cornernered the big black one and was really going at him.
Now we're not sure if it was all from the attack or if the big black one somehow got stuck somewhere but he had really bad like chafing on both of his sides. At this point he was just laying on the bottom of the tank so we took him out and put him in a tiny 30 liter cube (only thing we had) for him to heal. Over the next few days he didn't eat and the scales on his sides peeled off in chunks and you could see the flesh. We really thought he would die.
We kept a towel over the tank constantly so he wouldn't be sos stressed and after about a week he was still not eating but he was no longer just laying on the bottom, if we peeked we could see that he was moving around in there.
We figured the tiny tank must be depressive for a fish that was now almost 10 cm long so we decided to move him back to the big tank and at the same time take out the agressor (grey one) and put him in the small one for now. When we did this the big black one instantly perked up and swam around some, he ate food the next morning and healed amazingly after that, now almost a month later he is completely restored.
The big grey one we took back to the store a few days later. I actually called them beforehand since it was a bit of a travel for us and the guy there was very surprised at the agression. When we talked more back in the store he still said it was uncommon but he did notice that when we put big grey in their tank in the store he wasn't hiding at all even though he was new and kind of small compared to some of the fish in there. The owner had a theory that maybe we had too few fish for the size of the tank, he said when there are only three other fish it makes it easy for an agressor to have "full control".
We left there with two big (almost 15 cm) red shoulder severums and a pleco. Adding the new fish to our tank worked nice, everyone got along fine from the start.
Now after a few weeks the big black oscar is starting to get agressive towards the small black one and the small black one is yet again back to his corner. He never bothers the severums and I'm starting to think this is about size and he bullies the other oscars beause they are smaller. The white one always had it easier, she isn't bothered nearly as much and when she does gets chased ocasionally she just brushes it off. We had a theory that she's a female and the others are male and maybe that's why but we don't know.
How can we solve this? We feel bad for the small black one that mostly hides but we don't want to get rid of yet another big, beautiful fish. Would adding a couple more fish maybe help? Do we have space for it? (we would want one or two more anyway). And also what could cause the growth issues with the other two oscars? They do eat food at every feeding but they just won't grow. The white one also swims weirdly. She's like a bobber, her head almost always to the surface and she almost swims vertically. At first I thought it might be swim bladder but I have seen her "swim straight" so it's not impossible, she also has no issue actually acending or descending so the bouyancy doesn't seem impaired, it's just the constant weird angle.
