No Clue about Oscars

Question
QUESTION: My boyfriend and I are taking care of some Oscar fish that used to be our old roommates. When we found the fish the tank was extremely cold, and they acted like they were pretty much dead, somehow my boyfriend revived them and they've been acting fine ever since until recently. They both have great appetites, but recently the littler Oscar has been picking on the bigger one a lot. It will face him face to face and chase him around with his mouth open. The bigger one trys to get away, but the little one chases him around constantly trying to fight all day. Do you know maybe what could be wrong? They never used to fight.
ANSWER: Hey Amber,

First off, pat your boyfriend on the back! Oscars put under severe stress are generally difficult to fully revive. He seems like he's done a good job so far.

Now, for the aggression, and some general Oscar facts!

Oscar aggression can usually be defined as territorial. Normally, a larger male becomes the alpha in the tank, and will spar with the others, rarely. Every now and then there will be a brief chase, ending with the top dog floating proud, and his victim cowering in a corner, or off to the side. Other times, a male will chase and flaunt for a female when it's time to breed. If your smaller Oscar is the alpha (which is possible since the larger one could have taken longer to recover) the same things may be true. Either the larger is weaker, due to an infection you cant see yet, or the larger isn't male at all, but a female! Whichever the case, Oscars will typically chase each other, but they normally wont harm one another. Just keep an eye on them, and make sure one doesn't start getting cut up, or have it's fin's shred up. If the larger Oscar becomes very hungry and eats a ton, and starts to swell up... well then, you have a mommy to deal with! Some quick research on Oscar breeding will prove useful then.


Some general Oscar facts. Oscars are a type of Cichlid, whom prefer warmer, slightly salty water. A high 70*F to low 80*F is recommended for Cichlids. Typical diet for these large fish is about 70% meat, 30% veggie. If you feed your pair twice daily, which is common, feed them peas, or the tops of broccoli in the mornings, and krill, brine shrimp, blood worms, or cow heart in the evening. If beef is not your ideal fish food, brine shrimp are commonly known as sea monkeys and found just about everywhere. Most Cichlid tanks don't have a large algae problem, but if one develops in your tank, snails are the answer. No algae eater does well in warmer water (80*+) or salty waters (above 1.04), and Cichlids don't do well in water colder then 76*F or lower salt levels. Common Cichlid pellets can be fed, but fresh veggies and a frozen or freeze dried meat are needed once or twice a week. Oscars can be trained to hand feed, be pet, and jump for food as well! They typically will not hurt you if you stick your hands in the water, and can be very cuddly. Just wash your hands after, and rinse them well before (don't use soap on the rinse. Soap kills fish.) Frequent water tests to control pH, hardness, salt (hydrometers show salt level) ammonia, nitrite, nitrate, and other water quality factors will allow you to easily keep your Oscars healthy and in tip-top condition.

Well, that's about all the general information i have to offer at 12 am, but if you have any other questions, or feel that the larger fish is indeed sick, please feel free to ask a follow up with a bit more detail like water quality results (including salt level!) tank size, and if any, tank mates! Any plants, decorations, rocks, etc and filter size and type. All that information will give me a clear-er understanding of what's going on in your water.

Best wishes, and have a good night!

---------- FOLLOW-UP ----------

QUESTION: I'm so sorry to bother you again. I'm really getting concerned for the larger oscar. The little one is still constantly picking on it. I feed them brine shrimp, so it's not like they're hungry. The larger Oscar is really getting beat up, both front fins are looking chewed up, and he also has chunks of his scales missing all over his body. What should we do, they've never been like this with each other in the five years I've known these fish. Any advice? Should they be seperated? If so, how would we do that?

Answer
Hello again,

It sounds like you might need a tank divider. Sometimes with fish aggression, there is some underlying cause we don't always see. If i could sit infront of the tank for a couple hours, or a day or two, I might be able to figure out exactly why the little Oscar is the bully. But, since i can't, you can either a) sell one (or both) fish to a pet store (ask about a dollar an inch for the fish) or you can B) divide the tank. Tank dividers are generally cheap, and will allow you to separate the two fish until they heal up and / or you decide a better choice for them. My guess is you have two male Oscars in a tank too small for them. The little fish is the stronger one, because it recovered faster. the larger may have hole-in-the-head which will cause pits of decay in the face and head. This greatly weakens the fish, and leaves the smaller to become dominant. Adding plants, rocks to hide in, and other obstacles will also help once a divider is removed. Add some NovAqua or another conditioner that aids in fish regeneration. Because I can't physically see them in their environment, i can't offer too much more help then that. Separation seems like the key for now.

Best of luck, and hope all works out for you!