How To Setup An Oscar Tank (A winning setup)

Oscars are large, powerful fish. They need to be kept in an environment that matches their needs. The tank must be large enough, the water must be clean and heated, the decorations shouldn’t pose a risk to your oscar. Get the tank set up correct and your oscar will reward you by being a lovable pet that hopefully lives with you for many years.

I first started keeping Oscars around 30 years ago. Since then, a number of Oscars have passed through my fish room. Currently, I have a 180 gallon (680 liters) aquarium with a trio of Lemon Oscars in. It is a tank full of color, movement, and character!

What Size Tank Does My Oscar Need?

Large fish need large tanks! I often get asked ‘can I keep my oscar in a 40-gallon tank?’ ‘Can I keep my oscar in a 30-gallon tank?’ I have even been asked ‘can I keep my oscar in a 10 gallon?!’

The trouble is, that 2” fish you see in the fish store will fit happily into your smaller tank, but he will grow like a weed, putting on maybe an inch a month for the first 8 to 10 months. He will eat lots and poop nearly as much. Tank size and water volume are REALLY important.

The smallest tank I would ever recommend keeping an oscar in is a 55 gallon, and even then a large oscar can outgrow that. A 75 gallon is better and bigger still is better than that. I work on the rule of thumb that 75 gallons for the first oscar, then an additional 25-50 gallons per additional oscar is a good-sized setup.

I have a lovely trio of Lemon Oscars in a 180 gallon (680 liters) aquarium and they are doing really well.

When it comes to tank size, it is not just the swimming space we are looking at. Water volume is really important too. Oscars like to swim around their tank and they do appreciate the space, but the biggest problem is they eat a lot and they poop a lot, and the more water you have in the tank, the more stable the water parameters will be.



Fish waste causes the ammonia levels in your tank to rise. The filter turns that ammonia into less harmful nitrite and then less harmful still nitrate. Spikes of ammonia can quickly kill your oscar. The more water you have, the less likely an ammonia spike is.

A 55-gallon tank with a 50-gallon sump filter underneath is better than a 55 gallon with a sponge filter. Although the tank size hasn’t changed, there is nearly twice as much water when you include the 50-gallon sump.

Please don’t fall into the trap of buying a small tank today, and thinking you’ll get the bigger tank in a couple of months. Something always crops up before you buy the bigger tank.

The car will need fixing or the dishwasher will pack up. Before you know it a couple of months has become 6 months and your oscar is now struggling for space. I have seen countless pictures and videos of Oscars living in 40 breeders because their owners never got round to buying the bigger tank.

Start off with the right size tank, your oscar will thank you in the long run.

Make sure your oscar tank has a tight-fitting lid. Oscars aren’t the jumpiest of fish, but if startled they will leap. You don’t want to get home to find your oscar dried up on the floor.

What Is The Best Substrate For My Oscar Tank?

Your oscar doesn’t care what substrate your tank has. I have kept Oscars on gravel, sand, crushed lava rock, and in bare-bottomed tanks. It makes no difference to the fish. I wouldn’t recommend going for anything too large and coarse as food can fall between the pieces where it will rot down. Regular gravel is good for the job.

You won’t be growing any real plants, but if you have artificial ones, make sure your substrate is heavy enough to hold the plants down. Artificial plants in the sand for example will constantly be floating on the surface.

If you are not sure how much substrate your new Oscar aquarium will need, why not check out my article How Much Substrate Does My Aquarium Need?



Oscar Tank Decorations

Don’t spend too long aquascaping your oscar tank. I can tell you from many years of experience, your oscar will soon rearrange the decorations how he wants them. Whether you choose rocks or a castle or a SpongeBob pineapple house, I recommend making sure it can’t topple over and damage your tank or your oscar.

When I set up a new tank I always start with a layer of egg crate (sometimes called lighting diffuser) which sits directly on the tank bottom. Next in are the rocks. By placing them on the egg crate and putting the substrate around them rather than under them, the rocks won’t fall over if your oscar tries to dig under them.

Never stack rocks or decorations up. Oscars are both strong and clumsy. That pile of rocks will be over in no time and may either break your tank or hurt your oscar.

Oscars aren’t cave dwellers, but they do sometimes like to get away from the world. We have had great success in the past with large, terracotta plant pots laid on their sides in the tank.

The pot will create a cave that the Oscar can retreat into. Make sure you place something on either side of the pot, such as good-sized rocks, to stop your oscar from moving the pot around.

Bogwood makes a great addition to an oscar tank. You should however try to choose a piece that doesn’t have any sharp bits sticking out. If your oscar decides he wants to whip across the tank, usually at feeding time, it is all too easy for him to gouge his eye or cut himself on a sharp stick.

Bogwood makes a good choice of decoration for a second reason, tannins! Bogwood, especially a new piece, will turn your tank water into a lovely weak tea color. Your oscar will feel right at home. Unfortunately, we fish keepers prefer our tank water crystal clear.

Best Filter For An Oscar Tank

Oscars are messy fish. They eat a lot, and much of what they eat passes out through their gills. Oscars have teeth in their throats that help break up their food before they swallow it.

Unfortunately, this means some of the pellet food they ‘chew’ comes out of their gills as a cloud of uneaten food. As they eat a lot, they also poop a lot. All this poop and uneaten food need to be removed from the aquarium and it is the filter’s job to remove it.

I almost always recommend either a large canister filter or a sump with oscar tanks. Hang on the back filters make a great addition too, but are usually too small to handle the whole filtration alone. Other filters like internal power filters or sponge filters are good for smaller community tanks but aren’t really suitable for an Oscar tank.

I currently use various Fluval and Eheim external filters. An external filter draws the water out from one end of the tank, passes it through various different media inside the canister, and then returns the water, usually to the other end of the tank. This method gives great water circulation. A good canister filter should turn your entire tank water over around 4 times per hour.

I recently wrote an article which looked at the question Are Fluval Filters Good? It has some great information about the whole Fluval filter range.

Does My Oscar Tank Need A Heater

Oscars come from tropical climates. They need warm water to survive. Oscars like their tanks to be 75 to 81 (24 to 27). They can tolerate the temperature slightly above or below, but it’s best to shoot for a temperature in the late ’70s (around 25 DegC).

The problem with aquarium heaters is they are so fragile. The glass tube that encloses them can easily be broken by a falling rock or decoration, or by a large oscar crashing into them. I always try to put heater guards around all-out heaters.

Recently I have started to switch to the Fluval LED heaters as they come with a built-in heater guard. They are slightly more expensive, but we think they are worth the extra, just for the peace of mind.

In Conclusion

Providing you choose a suitably sized tank, make sure the décor can’t hurt your oscar, select a good filter and protect your heater from being broken, your oscar won’t care how his tank is set up. If you like a brightly colored castle or a diver with air bubbles coming out of it, then go for it.

If you are enjoying looking at your oscar tank, there is a greater chance of you spending more time with your oscar, which in the long run, will be good for your Oscar’s wellbeing.


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
Editor

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