Why Does My Oscar Have White Spots (And How Do I Treat Them)?

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Oscar fish are probably one of the most widely sold fish in our hobby. It seems like at some point everyone has owned an Oscar. It is probably thanks to their big puppy dog eyes or the fact they have bundles of personality. Whatever the reason, many of us see our Oscars more like pets than just another fish.

White spots on an Oscar fish are symptoms of a disease called Ichthyophthirius multifiliis, which is often shortened to Ich. Ich is highly contagious and, left untreated, can spread to all the fish in your aquarium. Ich can kill an Oscar if treatment isn’t forthcoming.

I have kept Oscars for as long as I can remember. I currently have a 155 gallon (600 liters) with a trio of Oscars in it and it is one of my favorite aquariums. One of the major attractions of Oscars is how hardy they are.

However, even a fish as hardy as an Oscar can occasionally become sick, and getting white spots is surprisingly common.

Why Does My Oscar Fish Have White Spots?

Oscars are hardy fish and they can live for 10 years or more in the right conditions. This hardiness means Oscars don’t often become sick, but when they do, they can become really sick, really quickly. Ich, or Ichthyophthirius multifiliis to give it its scientific name, is fairly common in Oscars who are stressed or have had their immune systems compromised.

The white spots you see on your Oscar are actually cysts that form when the parasite burrows into your Oscar’s skin. Initially, your Oscar may only have 1 or 2 white spots on its fins or body but left untreated those spots will quickly multiply until they overwhelm your Oscar.

A number of years ago, a buddy of mine was breaking down one of his tanks and I agreed to take an Oscar from him. I thought he was an experienced aquarist, so I didn’t bother to quarantine his oscar.

Unfortunately, the oscar already had Ich, and it infected my whole aquarium. Luckily I noticed the spots within a couple of days, so I was able to treat my aquarium and I didn’t lose any fish.

What Is Ich?

The white spots you see on your oscar aren’t actually the parasite, they are cysts caused by your Oscars immune system as a reaction to the parasite having burrowed into your Oscars skin.

Once the parasite is under the Oscar’s skin, it will stay there for a few days, gorging itself on the Oscar’s blood. Once ready, the parasite will drop off the Oscar and sink to the substrate where it will sit for a few days whilst it multiplies into hundreds more parasites. These ‘babies’ are known as tomites.

Once hatched, the tomites float around in the water column looking for another host fish and the process starts all over again.

What Are The Symptoms Of Ich In An Oscar Fish?

There are two main symptoms to look out for if you suspect your oscar may have Ich. They are;

  • White spots on the Oscars body, fins, or tail
  • The Oscar rubbing itself against rocks, decorations, or the aquarium substrate

White spots

At first, an Oscar may only have one or two spots. These often go unnoticed. The white spots look like small bits of sand or grains of salt. The number of spots can rapidly increase if left untreated and an Oscar can quickly be covered in spots over its entire body.

Rubbing against rocks and decorations

Some scientists believe the white spots may be itchy to the fish, much like a mosquito bite on a human. The rubbing action may be the Oscar trying to relieve the itchiness or rub off the cysts.

How To Treat Oscar Fish With Ich

Fortunately, there are a number of good Ich treatments on the market.

Personally, I have had good success using Ich-X which is made by Hikari (I usually just buy this one from Amazon.com). The instructions for Ich-X are fairly simple, you just add 5ml of Ich-X for every 10 gallons (38 liters) of aquarium water.

If you are based in Europe, eSHa 2000 is a really effective treatment for whitespot.

Please be aware, Ich parasites can ONLY be treated when they are in the water column. There aren’t any Ich treatments on the market which will attack the parasite whilst it is under an Oscar’s skin. Bearing this in mind, you may need to treat your Oscar tank more than once to make sure all the parasites are killed.

Can You Treat Oscars With Ich Without Using Chemicals?

Sometimes people don’t wish to use chemicals in their Oscar aquarium, or maybe they live in a location where they don’t have access to good Ich medication. Either way, if you need to treat Ich without chemicals, use the following method.

Water temperature has an effect on the Ich parasites’ life cycle. The warmer the water, the shorter the time it takes for the parasite to go through its life cycle. Increase the water temperature of your Oscar tank to between 80°F and 82°F (26°C and 28°C). This increase in temperature will mean the parasites spend less time under the Oscars skin and more time in the substrate multiplying.

After increasing the water temperature, start a regime of gravel vacuuming the substrate in your aquarium EVERY day for 7 to 10 days. By vacuuming every day you remove all the parasites which are in the process of multiplying.

Providing you are fastidious, you should manage to remove all the parasites.

How To Prevent Ich Entering You Oscar Aquarium?

As with so many Oscar-related pests and diseases, prevention is better than cure. If you can stop Ich from entering your aquarium in the first place, you won’t have to worry about having to treat your Oscars.

To prevent Ich from entering your tank, always do the following;

  1. Quarantine all new fish for at least two weeks prior to adding them to the Oscar aquarium
  2. When the new fish is in quarantine, treat with Ich-X as a precaution
  3. Maintain good water quality in your Oscar aquarium at all times by carrying out regular water changes
  4. Vacuum the aquarium substrate during each water change to ensure any parasites that survive quarantine are removed.

Ich is extremely prevalent in the aquarium hobby, so you should always assume your new fish has Ich, and treat it during quarantine to make sure the Ich doesn’t make it into your aquarium.

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In Conclusion

Ich is highly contagious and can be very serious if left untreated. However, there are a number of good treatments on the market, and it is possible to prevent Ich from entering your display aquariums in the first place.

Ensure you quarantine all new fish for at least 2 weeks, and make sure you treat your Oscars at the first signs of any white spots.

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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