How Long Can My Oscar Go Without Eating?

A small, but healthy juvenile oscar can easily go a week to 10 days without feeding. A large, healthy adult can go 2 or 3 weeks without eating. This doesn’t mean you only have to feed your oscar twice a month, but it does mean we don’t need to go into panic mode if they refuse a meal or two. If your oscar has stopped eating unexpectedly, it is important to try to establish why.

Over the last 30 years, a fair few Oscars have passed through my fish room. I have kept almost every color strain on the market, but Lemon Oscars are probably my favorite. I currently have a 155 gallon (600 liters) aquarium with a trio of Lemon Oscars in it. It’s an aquarium everyone who comes to my fish room likes to watch.

It can be a worrying time when your oscar stops eating. We sometimes think of our fish like people, we think they must have 3 meals a day, plus snacks. The reality is, your oscar can go longer than you think without eating.

Eating Daphnia
Eating Daphnia

With our Oscars, we don’t even start to worry for the first 2 or 3 days. If, however it goes beyond the 3-day mark, we start to look for the reasons why our oscar has decided to go on hunger strike.



Why Has My Oscar Stopped Eating?

I addressed this very subject in another article which I wrote a couple of months ago. That article is titled Why Has My Oscar Stopped Eating?

We have all made the classic mistake of buying a 10lbs bag of pellets because they were a bargain. You feed those pellets by the hand full three times a day because it feels like you have an endless supply.

The problem is, your oscar doesn’t want to consume 10lbs of floating pellets in a month! He wants variety. He wants frozen bloodworms or daphnia; some days he might fancy some sinking pellets or a nice block of Repashy.

If your oscar hasn’t shown any interest in his food for a couple of days, order something different for him to try. Amazon, for instance, has a massive selection of foods to try.

I recently wrote an article titled What is the Best Food to Feed my Oscar? which has some good Oscar food ideas.

Is Your Oscar Unwell?

So, you’ve tried mixing his foods up but he still won’t eat. Next, we need to check if your oscar is unwell. Take some time to really look at your oscar. Are there any signs of illness? White spots, cotton wool-like fungus, worms protruding from the oscar vent? These are all signs your oscar has stopped eating because he is unwell.

Take a look at our Oscar Health Guide to work out what might be the problem. Swift treatment should lead to a swift return of your Oscars appetite. If there are no outwards signs of illness, could your oscar have internal parasites?

Oscars that have just come into your care, especially if they are imported from the wild, may have internal parasites like tapeworms. These worms consume the food inside the oscar before they can. Eventually, your Oscar’s stomach will fill with worms, putting him off eating. Deworming your Oscars with a product like General Cure from API will sort him out pretty quickly.

Are Your Water Parameters Off?

Fish need their water to not just be physically clean, but also chemically clean. If your tank has a build-up of ammonia, nitrites, or nitrates, it may be enough to put your oscar off his food. I use the Master Test Kit by API. (I bought this one from Amazon) to check my water quality.

Ideally, your test kit should read 0ppm ammonia, 0ppm nitrite, and 40ppm nitrates or less. 0ppm nitrate is the ultimate reading, but tricky to achieve with a large, heavy feeding fish like an oscar.

A large water change (50%-75%) should be enough to reset your water parameters in the short term, but you will need to work out why they went off in the first place.



Has Your Heater Stopped Working?

Oscars need warm water, they come from tropical rivers. One thing we as fish keepers often overlook is checking our heaters are working. Oscars like their tank to be in the 75 to 81 (24 to 27) range.

A tank that is too cold, or too hot, will have an effect on your oscar. They can handle temperatures above and below their ideal range for short periods, but in the long run, it will affect their appetite and their health.

Remember, a heater can get stuck ‘on’ as well as ‘off’, meaning your oscar may be slowly cooking!

Has Your Fish Food Gone Off?

Much like with human food, fish food will go off if kept long enough. Most people wouldn’t consider opening a bag of chips, eating one, then closing the bag and repeating the next day for weeks until the bag is finished. The chips would go stale and be unpalatable.

That is exactly what we do with our fish food. Often we buy the largest container we can because it is cheaper, then we plow through it for the next two years, opening the can 3 times a day, exposing the food to air.

Once your Oscars food goes off, it may be unpleasant, as well as unhealthy for your oscar. It is better to either buy smaller containers more often or, if the large pack is too good a bargain to leave, tip it into a number of separate containers or food bags and just work through one batch at a time. That way, you have one tub on the go and another couple in storage ready.

In Conclusion

Oscars are generally strong, hardy fish that can go days, possibly weeks without eating when they have to. If we go on a 1-week vacation, we don’t even worry about asking someone to come in and feed our Oscars. They will be just fine.

It is important however to establish WHY your oscar has decided to stop eating. It is usually water quality-related. Carry out a water test as soon as possible and make the necessary changes to adjust the water quality.

Frozen fish foods such as bloodworm and brine shrimp will usually tempt all but the most stubborn oscar back into eating. Don’t go into panic mode and start chucking one of every food you have into your Oscars tank. Offer him some food, if he doesn’t eat it within a few minutes, remove the uneaten food from the tank and try again tomorrow. It is very rare for a healthy oscar to starve himself for too long.


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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