The Oscar cichlid is one of the oldest and most popularly kept fish in the aquarium hobby. Properly kept and maintained, it is a large, magnificent fish that will become a member of the family, as they definitely will greet their owners in just about the same way as a family dog. 

That said, they do require quite a bit of care to thrive, which should be the goal of every fish keeper. Oscars are most definitely NOT a "beginner's fish". There is nothing sadder than the sight of an Oscar that has been kept in less than pristine conditions. So, with that in mind, let’s review what I have found that they require to look and do their absolute best:

Aquarium Size 

This is where a LOT of people go wrong. Do NOT purchase a small aquarium with the intention of going out and purchasing a larger one later. Aquariums should be purchased with the adult size of the fish you want to keep in mind. When you want to keep a species of fish that are as robust as Oscars are, you need VERY spacious quarters.  People frequently make the mistake of thinking that the cute little fish they just purchased will be OK in that 30GL aquarium “for now”. No, they won’t.  Oscars are a species that grows F-A-S-T,  before you know it, you've got to purchase a bigger aquarium.  Stocking for large cichlids like Oscars is ALWAYS based on the maximum ADULT size of the fish to be kept. Regardless of present size, the absolute bare minimum aquarium for an Oscar, (and there is a caveat that comes with this) would be a 55 gallon aquarium. Keeping an Oscar in a tank of this bare minimum size also means NO tankmates AT ALL, very little or no decoration, extremely efficient biological and mechanical filtration, & VERY frequent partial water changes, as in 75% every other day. A 75GL tank would be better, 90GL is ideal, and this is just for one Oscar. The Oscar cichlid can easily get to be 14”+ in captivity (I personally have seen specimens in excess of 18”), & they produce copious amounts of waste. If you cannot afford or simply do not wish to have an aquarium of at least 55 gallons, do not consider keeping an Oscar. You are just setting yourself up for failure and heartache. There are several species of cichlid that will do well in a smaller tank, but an Oscar is most definitely NOT one of them.

Feeding/Diet 

Oscars are gluttonous fish, bottom line. They can “train” their owners to give them what they want and when they want it; they are also VERY messy eaters, as what they eat will be processed by the pharyngeal mill in their throat, which then comes out in a cloud of particles into the water column. They are usually not fussy about what they are fed, although some will turn up their noses at new foods or turn down usual offerings if given live food (like feeder fish, which will be discussed later). The best food for a staple would be a high-quality pellet, mixed in with the feeding of freeze dried krill soaked in a liquid vitamin. This is to ensure that they get the vitamins they need. The lack of vitamins is thought to contribute to HITH so adding extra vitamins to food is crucial to their long-term well being. Some owners even go so far as to make their custom foods for their fish, which is OK and can then control what goes into their fishes diet. As far as live food goes, there are a few live foods that are OK to give your Oscar, such as earthworms, crickets, and mealworms, but NEVER, EVER, EVER give your Oscar feeder fish or any aquatic or semi-aquatic live foods of any kind. Feeder fish are raised by the billions in outdoor ponds or indoor vats; they are known to  carry a plethora of parasites and pathogens. ( I have been to a farm where feeders were being raised...the smell would knock you out!!) Some people raise feeder fish in their homes to give to their Oscars, but unless you can guarantee absolutely sterile laboratory conditions, this is an unhealthy practice, & I would strongly advise against doing so. The chance of spreading disease or contracting a parasite is too great. With all the available prepared foods out there, & the fact that there are safe live alternatives to feeder fish, giving feeder fish is unwise and unnecessary. 

Maintenance/Filtration 

Oscars are a large, robust fish, and are one of the messiest cichlids out there. They are messy eaters, defecate & urinate frequently and what they leave behind is quite large!! It is therefore very important to have an efficient and mature biological filter accompanied with extremely efficient & powerful mechanical filtration that will remove solid waste. A combination of large HOB filters combined with a canister and/or a “sump” style wet/dry will work quite well. You simply cannot mechanically or biologically over-filtrate any cichlid tank, & that applies doubly for Oscars!!

Now let’s discuss water changes. Water changes are the life-blood of this hobby. You can have the most powerful & efficient biological & mechanical filtration that money can buy.....you still have to do WC's!!! When dealing with WC’s for Oscars(or just about any cichlid for that matter!!),when you think you’ve done enough, think again. Oscars are an Amazonian cichlid species genetically, and as such, demand pristine water quality. One of the easiest and best ways to accomplish this is to simply do frequent, large water changes. (I would recommend to anyone to get one of the very easily available water-changing devices on the market if you do not have one. It will make do this necessary chore a breeze) Be extremely aggressive about your WC schedule, you simply can never do enough to keep them in prime condition. I would recommend no less than 75% 1X per week, bare minimum; 2X would be better ( this is in conjunction with a thorough gravel or sand vacuuming each time). We have all seen pictures and videos of Oscars who have contracted HITH; one of the main, if not the singular cause of Oscars getting HITH/LLE is simply being kept in sub-par water quality for an extended length of time, due to the fishes owner not performing this necessary chore enough. If want to keep your Oscar healthy, change that water often!!

Tankmates 

Oscars, as with most cichlids really do not require tankmates. They do not get “lonely”, they do not make "friends".; in fact they do not appreciate the company of conspecifics (or heterospecifics for that matter) outside of breeding. If you want to have a tank with an Oscar or 2, or have a mixed species tank, be prepared to purchase an aquarium at least in excess of 150 gallons, and that’s just for 2 or 3, depending on adult size of the species in question. Oscars do make great "pet" fish when kept singly. In all reality, keeping semi-aggressive to very aggressive fish in one aquarium is really a crapshoot; it might work, but chances are, it will NOT. Another point I must make is that I personally do not recommend keeping SA & CA (or African) cichlids together. For the most part, (and beyond water chemistry issues) SA cichlids do not have the jaw strength not the dentition (nor the “kill them all” attitude that most CA cichlids have!!) to be able to defend themselves and usually wind up mauled or dead. Tankmates must always be chosen with care & you must be prepared to separate them, give the new fish a home of its own, or re-home the new fish, as it may not work out as you intended.

PH & Temperature 

As discussed earlier, Oscars are Amazonian in ancestry; when I kept Oscars, I always kept them like Discus & Angelfish,  that means warm water (80-84F)  soft, acidic PH (PH values of 6.0 to 6.8). Oscars, like other fish, can adapt to a wide range of values and do well, but to actually thrive and do & look their absolute best, they should be kept them at these values and temperature. They thrived in these conditions. I recommend anyone thinking about keeping them to give it a try; you will be amazed at the results!

Oscars are an amazing fish, when kept properly. They do require quite a bit of care to do well, but they truly become a pet and are worth every bit of effort their owners put forth.