Hello, I have a red tiger ocsar about 9-10 inches long, I have had it since it was a baby about a year ago, it has suddenly started to go up to the glass turn a green colour (not black like usual) and try and swim as fast as it can while flaring its gills it will also shake very vigorously. It also chases the other fish when it gets in one of these 'moods' - does anyone know what this could be?
I also have a breeding pair of severums, a silver shark, 5 koi angels and 1 senegal birchir in with it.

Thanks all.

welcome to oscarfishlover

Sounds like it's approaching sexual maturity to me. Many creatures act strange at this time in their lives, including fish. Remember that hormones change so this can affect their behaviour. To be quite honest, I can't think of any other reason why your fish would behave like this.I have got four Oscars in my 300 gallon tank, they have reached maturity and are showing similar signs to your fish. I've had a breeding pair of Oscars before so I know what the signs are.

I would check the water conditions, fish often acts strange and swim around the tank very quickly if there are toxins present. However, since you haven't mentioned anything about the other fish acting strangely or showing signs of ill-health, I doubt it is this.

i have an albino that does the same thing. i was thinking it had something to do with reaching sexual maturity but im not 100% positive on this. maybe hes looking for a mate. but the first thing i think you should do is to test your water and make sure that it fall in the right parameter: ammonia 0 nitrites 0 and nitrates less than 40


btw welcome to the site

I have an oscar who is doing some strange things the last few days. He comes to the front of the tank and opens it's mouth and shakes back and forth, stops for a few seconds then does it all over again then goes to the bottom of the tank facing the front and shakes the rock everywhere on the bottom of the tank. Very wierd but hella funny at the same time. Does anyone know what he is doing?

Good day! The size of your oscar is already in the range of sexual maturity. Please check if there is a lump on the lower jaw, which is the first sign of maturity. They will try to move everything at the bottom of the aquarium. If you have loose stone or gravel inside, they will lift them up and release, having a tendency to break glass flooring of your aquarium if ther is no substrate.

The first sign that I observed with my oscars was that they keep on kissing each other that looks like fighting, swim along side, then wiggle. After establishing their territorial place, will drive away everyone that comes near to that place.

However, if you don't have a pair, perhaps, they will act differently.

There is a lump on the albino oscar but no lump on the orange one. He shakes the bottom of the tank so the rocks are thrown out and there are spots with no gravel. And yes, these 2 seem to stay relatively close all the time....Uh oh????