Choosing Suitable Tank Mates
I think it's probably worth mentioning that some people are under the misapprehension that Oscars get lonely on their own. This is completely untrue, an Oscar fish is more than happy having the whole tank to itself, in fact it would probably prefer to be on its own.
There are a few very important rules that you should follow before introducing fish in with your Oscars. First and foremost you must choose fish that are not going to become an instant meal as soon as you put them in with your Oscar fish. Oscars have got big mouths and they also have eyes bigger than their belly, they will try and eat just about anything they can get into their big gobs. Tank mates should start at around 5 inches, anything smaller than 5 inches could well be at risk once your Oscars reach adulthood. Tank mates must be capable of competing for food, Oscars are extremely greedy and will do their best to eat any food you put in the aquarium. If a tank mate cannot compete for food then it may well starve. Shy fish will have a hard time if the Oscars constantly harass and chase them around the tank. Whereas Oscars aren't the vicious killers that some people like to make out, they certainly can be bullish towards other fish living in the aquarium with them, so choosing tank mates that have the natural ability to give Oscars a wide berth should fit in nicely.
One of the successful but not absolute guaranteed ways of choosing suitable tank mates is to look at the natural way they live. Oscars for instance spend a lot of their time swimming mid-surface and towards the surface of the water. Oscars are not primarily bottom dwelling fish, although they will explore just about anywhere in the aquarium. Choosing tank mates that spend most of their time foraging around the bottom of the aquarium will most likely keep themselves to themselves and not get in the way of the Oscars. Catfish for instance feed on the bottom and hide amongst rocks, whereas these are primarily nocturnal fish, you can sometimes keep them very successfully with Oscar fish. Jurupari are another bottom dwelling South American fish that make superb tank mates for Oscars. Silver Dollars are mid-water dwellers and are on the move constantly, these make superb tank mates for Oscar fish, in fact they are probably in my opinion in the top five of suitable tank mates for Oscar fish. A lot of people like to introduce various different species of cichlid as a tank containing different varieties of cichlids can looked absolutely stunning. However one important thing to remember is that cichlids can be troublesome when mixed together, so if you do want to mix various types of cichlids, please research research research.
Oscars are normally semi-aggressive so in most cases you won't encounter too much aggression. However if you are going to introduce cichlid tank mates, you may be wise to opt for the slightly smaller cichlids species. Cichlids such as Firemouths, Jack Dempsey's Severum, Blue Acara, Convict Cichlids, Jade Eyed Cichlids are all fish that will live with Oscars without any problems. You are probably best to avoid the larger cichlids such as Jags, Peacock Bass, Terrors, Texas cichlids for example. These type of cichlids get fairly large and have a fiery temperament. Some terrors can be best described as being absolutely vicious and are definitely fish to be avoided. Just be aware that the majority of cichlids can be temperamental, no matter how big they are. So whatever Cichlid fish you intend on putting together, be very careful which ones you choose.
I now keep just one 12 inch Leporinus with four Oscars ranging from about 11 inches to 13 inches, three of the Oscars seem to get on well, the fourth one came from the same batch as the two red Oscars and has always been a little smaller. It's had quite a few health problems over the last six years but is now perfectly healthy, however it appears to be the runt of the litter and to a certain extent has been excluded from the group. It's quite common in nature for the weaker ones to be kicked out, after all it's an animals job to reproduce, female cichlids will choose healthy males and probably either ignore, or ostracise any that are not up to scratch. The Leporinus is probably one of the best tank mates I have ever had, the Oscars pay absolutely no attention to it and vice versa. The Leporinus doesn't feed on floating food, they much prefer to either feed on food that is sinking slowly, or feed on sunken food lying on the bottom.
It's easy to help yourself, we've all had to research our hobby at some time, get yourself a good book, the published by Interpet is a very good start, this book will give you all the information you need, where the fish comes from, what temperament it exhibits, what it feeds on etc etc. This is one of the first books I ever purchased, it is absolutely invaluable in my book collection and continues to help me.
Leporinus make wonderful tank mates
Groups of Silver Dollars looks stunning in an aquarium
A few suitable tankmates
Silver Dollars - Metynnis hypsauchen - 6"
Silver Dollars don't like being on their own so should be kept in groups of a minimum of three. They are extremely placid and make excellent tank mates. Make sure that you have a supply of vegetarian food if you keep silver dollars more info...
Severum - Heros Severus - 12"
Severums really do make excellent tank mates for Oscars as they can stand up for themselves perfectly okay and are more than capable of competing for food more info...
Jade Eyed Cichlid - Cryptoheros spilurus - 6"
The Jade Eyed Cichlid is a Central American cichlid. Whereas I'm not in favour of mixing fish from different parts of the world, this was one cichlids that did work well with my Oscars.
Black Banded Leporinus - Leporinus fasciatus - 12"
I absolutely adore my Leporinus, they are not aggressive and keep themselves to themselves. However they can occasionally nip at other fishes fins but it's not something you should worry about. They can be a little timid and skittish so any sudden movements in front of the tank will startle them. These fish absolutely love peas
Jurupari Earth Eater - Satanoperca jurupari - 10"
These Earth Eater fish are very placid & like being in groups, from my experience they don't do very well on their own. They will eat sinking food and blood worm so can compete for food easily. If you have a group of them they are fantastic addition to your aquarium
Blue Acara - Andinoacara pulcher - 8"
These little chaps can be fairly aggressive so will stand up to Oscars. My advice would be to purchase these as adults as they can find it difficult to compete for food when they are very small, especially if you got more than one Oscar.
Firemouth - Thorichthys meeki - 8"
This relatively small cichlid that doesn't normally exceed 8 inches is another fish that will more than stick up for itself if sharing a tank with an Oscar
Plecostomus - Hypostomus plecostomus - 18" +
Often abbreviated to Plecs or Plecos, these bottom dwelling fish are very popular as people buy them for their ability to cleanse the tank of algae. However, please be aware that some species of Pleco can well exceed 12 inches, in fact some species such as the Sailfin and Common can even exceed 18 inches. The larger specimens of Pleco need large aquariums, in excess of 100 gallons so please don't buy these fish unless you have the facility to house one properly
Chocolate Cichlids - Hypselecara temporalis - 12"
Chocolate cichlids come from South America. Even though these cichlids can easily reach 12 inches, they are actually very peaceful. So long as your Oscar isn't aggressive, and your aquarium size permits, a Chocolate cichlid could make a very good tank mate
Obviously there are many more fish that you could put in with your Oscar, these are just a few Examples of the more common tank mates that people keep with their Oscar fish.
The sizes quoted on this page are meant to give you an idea of how big these fish can get. It isn't guaranteed that these fish will get this big in your aquarium. If you are unsure about what fish to mix with your Oscars then please visit our forum and seek advice...
Fish Can Often Be Territorial
Rather like cats and dogs who guard their territory, many fish, cichlids especially will often lay claim to an area of the aquarium and will get very aggressive towards other fish encroaching on "their patch". One example would be my 5 inch Blue Acara, he has decided that the area at the back of the tank behind a large piece of wood belongs to him, he very rarely ventures outside of this area even though his tank is 8 foot long and 350 gallons. If any of the other fish, including Oscar's enters this area, he will try and see them off and isn't happy until they are gone. So the point I am trying to make is that if you are going to keep different species of fish together, especially various types of cichlids, trying to keep them in a small environment could be fraught with difficulties.
You have to remember that the total body mass of of fish will determine how much bio-load will be put on your biological system. To put it simply, the amount of ammonia that your nitrifying bacteria is able to process. If the bacteria can't keep up with the waste that your fish produces, dangerous toxins could well start building up in the tank water. This is where health problems could start.
We have already established that 55 gallons is the absolute minimum that you would want to keep an adult Oscar fish in. Two Oscars will obviously roughly twice the space, definitely no less than 100 gallons. Let's go back to the total body mass of a fish. An adult Oscar can be very big, it has a large body mass. Not only do Oscars grow to quite impressive lengths, they also have deep bodies as well. Oscars normally only reach around 12 inches in captivity. If this is the case, you may calculate that half of 12 is 6 and determine that you can only have a couple of 6 inch fish.. This isn't necessarily the case. Let's look at pictus catfish for instance. These can reach five or 6 inches. That is half the length of a 12 inch Oscar. However, it is by no means as deep, in fact it, an Oscar is probably four times the height of the pictus catfish, so you can see that you could probably have four or five pictus catfish in with one Oscar as four or five pictus catfish will produce around the same amount of waste as one large 12 inch Oscar. In fact, I would say an Oscar of that size will produce a lot more waste. And since pictus catfish to do well in shoals, these make ideal tankmates, as long as they are adults are not small mouth size snacks. I have included a shortlist of other suitable tank mates, I'm not going to confuse you, after all this website is aimed at beginners so use your initiative, if you've got 100 gallons then it goes to say that you are okay with one Oscar and a Severum, it's as simple as that. It's not okay to put three Oscars and a Leporinus in a 100 gallon tank because there is not enough room.
Some cichlids can be very aggressive, so mixing them has to be thought through thoroughly. For instance, I wouldn't recommend putting a green terror in with your Oscar, that could well be a recipe for disaster. I have already mentioned that Oscars will eat anything that they can get in their mouth, so putting in a shoal of neon tetras would be a pretty stupid thing to do. Whatever you put in with them, make sure they are at least 4 in. long. Silver Dollar's, tinfoil barbs (not too many as these do get quite big) some species of cichlid are all suitable for a large Oscar Tank. I have got a jade cichlid and I have no problems whatsoever, it is a beautiful peaceful little fish.
There are various catfish which make suitable tankmates for Oscars. if you do choose a catfish, I would strongly advise you to go for a fully grown adult. Pictus catfish are common amongst aquatic enthusiasts and are a nice addition to any tank. These little catfish normally reach around 5 inches. If you do choose one of these, try and go for one that is at least 4 inches, preferably more.
Beware of Catfish
We already know that Oscars have got big mouths and they can get a lot in them. They are greedy fish and sometimes have eyes bigger than their belly. They will often grab hold of things that they have absolutely no chance of swallowing. The problem with some catfish is they have spines located on various parts of their body, especially on their dorsal and pectoral fins. These spines can be extremely sharp, some catfish have spines that are sharp enough to penetrate the bottom of somebody's shoe. What can happen is an Oscar grabs hold of the catfish, realises it can't swallow it and then tries to expel it. This is when problems can arise.
Fish normally swallow their prey headfirst so that fins such as a dorsal fin don't get stuck in their throat. Unfortunately, what goes down easily doesn't always come out as well. When the Oscar tries to expel the catfish, the spines can get stuck in either the fish's throat, or its mouth. In a lot of circumstances, the Oscar will manage to release the catfish. In a small number of cases, it just cannot budge it. When this happens, you have to take immediate action. If you are a confident person, remove the Oscar from its tank and take the catfish out of its mouth. If the catfish's spines have penetrated the Oscars mouth and you can't pull the catfish straight out of the mouth, you will have to remove the spines from the catfish. A pair of manicure scissors are excellent for this task, if you haven't got any of these to hand, something equally as small should suffice. Snip the spines and remove the catfish.
One of our own members had this exact problem. His Oscar tried to swallow a catfish and it got stuck. The spines actually penetrated the bottom of the Oscars mouth. He had to perform minor removing the spines from the unfortunate catfish, which meant he could remove it from the Oscars mouth. Luckily, the Oscar lived to tell the tale. So you see that choosing tankmates is very important. Oscars can and will try and eat their tankmates if they think it is a viable meal.
Check the Size
Fish shops are stocking more and more varieties of fish nowadays and quite often some very exotic species are finding their way into the UK. Before you purchase any fish it's vitally important that you know exactly how big it will get adult size. Plecos are are readily available in most fish stores and they are very cheap to buy. Unfortunately people are under the misapprehension that these are cleaner fish and will actually help keep your aquarium clean. The cheaper species tend to be the ones that get the biggest. Common, Sail Fin, Leopard plecs can all exceed 12 inches and quite often reach 18 inches in size. A fish like this can create an enormous amounts of waste which can pollute the water very quickly. Unless you have a very large tank than fish like these are probably best avoided. They may well eat algae and keep the glass clean, but what goes in has to come out and I can say without hesitation that you will spend more time cleaning up after the fish than it takes to wipe a bit of algae off the glass. There are quite a few species of plec, many of them don't exceed 8 inches in size and are much more suitable for the smaller aquarium.
Another South American fish that often turns up at fish stores is the Pacu. The Pacu is primarily a vegetarian feeder but will readily accept all types of food. These fish can reach 3 feet in the wilds and easily exceed 24 inches in captivity. They are suitable for large aquariums exceeding 100 gallons so they are probably best left where they are if you do come across one in your local fish store.