Why Has My Oscar Stopped Eating? (Explained)

Oscars occasionally stop eating due to illness, poor water quality, or because their food has become stale. Oscars may also stop eating due to boredom with their food or due to lack of environmental stimulation.

Eating Daphnia
Eating Daphnia

Over the last 30 years, I think I have kept just about every color strain of Oscar there is. I currently keep a trio of Lemon Oscars in a 180 gallon (600 liters) aquarium. It is a tank full of color, movement, and personality.

Oscar fish have tonnes of personality, that’s why we love them. They are a true wet pet! The problem is, all that personality can come at a cost.

Your Oscar can occasionally act like a stroppy teenager. Oscars can be moody and sulky and this can occasionally lead to them stopping eating.

Are Oscars Fussy Eaters?

It is not unheard of for Oscars to just stop eating, for no apparent reason. One day they are throwing back their food, making a mess all over the place, the next, they refuse to eat.

If your Oscar has stopped eating, the first thing to check is, has your Oscar just become bored of eating the same food three times a day?

You can try holding the food back for 2 or 3 days and then restarting feeding (don’t worry, Oscars can go for days without feeding). When you restart feeding, you may find things are back to normal.

If not, maybe try a different food. I recently wrote an article titled 10 Unusual Foods Your Oscar Will Actually Enjoy if you are looking for some fresh feeding ideas.



With my Oscars, I tend to have 3 or 4 different types of foods on the go at once. One feed will be pellets, the next maybe a frozen fish food. By mixing it up, we keep it interesting for the fish as well as giving them a mix of different sources of vitamins, minerals, and goodness.

I have always found these pellets I order from Amazon to be loved by all my Oscars!


https://youtu.be/lquPGCfvhEM

Has Your Food Gone Stale?

We often make the mistake of buying food in bulk because it can be cheaper to buy in volume. The problem is, if you have just 1 or 2 Oscars and you buy your food in a 20lb sack, it will take months, possibly years to get through that food.

Every day you open the bag to grab a few pellets out, letting in air and slowly making the food go stale. If you opened a bag of potato chips every day, removing 1 chip then closing the bag, it’s not hard to see those chips will go stale very quickly.

To solve the problem, either buy your fish food in smaller containers, or buy in bulk, but then portion the food into smaller containers like these ones.

Is There A Problem With Your Water Quality?

Oscars are messy eaters and require good filtration and regular water changes. I use a Fluval canister filter on my Oscar tank (more on Fluval canister filters in this article).

Oscars also require regular water changes to keep the nitrate levels down to a minimum. Water can look crystal clear, but may still be harmful to your fish. You should use a good quality test kit (I use the API Master Test Kits) to check for ammonia, nitrite, or nitrate in your aquarium water.

Tests kits produce results in just a few minutes and should become part of your fish care routine. If your test kit shows you have elevated ammonia, nitrite, or nitrate levels, carry out a large water change and re-test. On my Oscar tank, I change 25% of the water every week.

Has Any Of The Aquarium Equipment Failed?

One seemingly obvious, but often overlooked problem is a heater failure. If your aquarium heater has given up the ghost, the water may now be too cold for your Oscar. If the thermostat inside the heater has stuck ‘on’, the water may be too hot. Although Oscars can tolerate a fairly wide temperature range, 75°F to 81°F (24°C to 27°C) is ideal.

Temperatures on either side may lead to a downturn in your fishes’ health. Use a digital thermometer to check to water temperature.

Is Your Oscar Unwell?

Assuming you have ruled out the two possibilities above, take some time to sit and look at your Oscar. Does he look unwell? Are his colors faded? Is he breathing heavily? Oscars are kept in large numbers at both stores and wholesalers. If your Oscar is new to you, he may have picked up parasites on his journey to your aquarium.

If you’ve recently added new fish to your Oscars tank, they may have passed infections or parasites to your fish. Oscars can suffer from internal or external parasites. Take some time to see if you can see any signs of external parasites or infection.

Ich (Whitespot) is very common and will show itself as white spots all over your Oscar (see my article Why Does My Oscar Have White Spots? for more information about Ich). Fungus (white, cotton wool-like growths) on Oscars are also common.

For external diseases, I find Maracyn by Fritz to be very effective (check the current price of Maracyn here).

Oscars may also suffer from internal parasites, which you won’t be able to see just by looking. Tapeworms are easily picked up and can be hard for your Oscar to pass. They will eventually build up inside the Oscar, consuming the goodness from the Oscars’ food and eventually killing the fish.

Over the years we have had good luck treating our Oscars with Paracleanse from Fritz. In fact, I now treat all my fish with Paracleanse when they first arrive in my fish room, just as a precaution.

Does Your Oscar Have Hole In The Head Disease?

Another problem Oscars are prone to is Hole in the Head (sometimes referred to as HITH). In short, there are many potential causes of Hole in the Head. Parasites, poor water quality, lack of variety in feed, and stress are all potential factors.

Hole in the head symptoms includes pitting on both the head and lateral line. These holes will start off small but will grow over time if treatment is not swift. A hole in the head can be a symptom of one or more of the problems highlighted above.

A combination of working through each of the items above, correcting any issues as you go, plus treating with metronidazole, should stop the Hole in the Head from getting worse and help your Oscar get his appetite back.

In Conclusion

If your Oscar has been off his food for just a couple of days, with no obvious signs of why don’t panic too much. After 2 or 3 days, work through the points above and see if one or more of them are causing your Oscar’s lack of appetite. In the past, I have found boredom from eating the same food day in day out to be the cause, and feeding a good variety will keep your Oscar guessing what food is for lunch today.

Take a look at my ‘10 Unusual Foods Your Oscar Will Actually Enjoy’, article, you might be surprised the variety Oscars will eat!


About the Author

I’ve been keeping, breeding, and showing tropical fish for nearly 30 years. Over that time I’ve done it all! I’ve had great success and I’ve made some really foolish mistakes (like the time I bought an Asain Walking Catfish). Read more…
Richard James
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