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Discussion Starter · #1 ·
an article i wrote, still has several grammar mistakes and more content will be added to it, nonetheless here is if anyone is interested :)

Walk into a pet shop, and your bound to see oscars. Unlike most fish which will be boorishly laying on the bottom, oscars will usually be at the front of the glass begging for attention! Because of this puppy-like behavior, oscars are one of the most popular fish out there- but most don't realize their potential to turn into 12'' monsters!

Domain: Eukarya
Species:Astronotus ocellatus

Your oscar can be kept in as little as a 10 gallon tank when young, but soon, you will need at least a 75 gallon tank. Optionally, you could buy a 55 gallon tank and use that, but you'll need to keep decor on the low-down since 55 gallon isn't a whole lot of space.

Now that you gotten your 75 gallon tank, you'll need to cycle it. But first, you need a water test kit. You can find one in virtually and pet of fish shop. Be sure to buy a liquid kit that contains at least the following: ammonia, nitrite, nitrate, pH. While your at it, buy a couple guppies, goldfish or black-skirt tetras too. Now that you've got your test kit and a bag-o-fish, plop your fish in the tank. Your probably asking, "Now why did I just buy a bag of guppies? I wanted an oscar!" Well, don't worry, we'll get there. Your going to have to go through a process called cycling. You'll keep and feed your fish for about a month (40 days) will monitoring your water parameters. Simply, the fish produce waste, which produces a harmful toxin called ammonia. Once ammonia is present, beneficiary bacteria will start sprouting up to feast on this ammonia. Then, the bacteria create another waste produce, the slightly less harmful nitrIte. After nitrIte is present, new bacteria come and start feasting on the nitrIte. Then, they make a waste product called nitrAte, which is much less harmful then nitrIte and ammonia. However, in high amounts it can be harmful, so you'll remove it by 20% water changes weekly. Now, you'll be checking your water parameters to see when your tank has cycled. You'll have noticed ammonia and nitrIte become significantly less over the 40 day period. Once this has happened, get rid of the fish, do a large water change (30% at least) and add your oscar! Now, what kind of oscar should you get???

There are quite a lot of different varieties of oscars in the hobby today, here is an outline of just a few:

This is by far the most common variety of oscar your going to encounter. They are "trademarked" by several stripes of red, brown, and black.

Perhaps the second most common variety, this kind of oscar inhibits a brown head and an otherwise reddish/orange body.

This is an oscar characterized by being mostly white, due to not albinism, but more often lutinosism. The difference is that albino oscars will be pure white with red eyes, and lutino oscars will have some coloration and brown/orange eyes.

Basically, just an oscar from the wild. They or often drab, but nonetheless quite often sought after.

A wild oscar past F4. Inhibits no special "features" or coloration.

A red oscar bred to contain "goldish" coloration.

A lutino oscar bred to contain yellow coloration

This oscar was bred to be half black, and half other coloration. Unfortunately none remain in the hobby today.

DYED OSCARS (Strawberry, blueberry, pumpkin, etc.)
These are oscars injected/dipped in a dye. This is very stressful to the fish and is quite harmful to it in the long run, causing a weakened immune system and subsequent, a shortened life. They can come by the name of strawberry, blueberry, even halloween or "pumpkin" oscars. You'll notice green and red dyed ones show up around Christmas, while orange ones show up around halloween. Oh, and DO NOT BUY THESE FISH! You will regret it.


Generally, you should be feeding your oscar something called a 'staple' diet. A staple diet is what most of your oscar's diet should consist of (generally somewhere around 50-80%). Many oscar keepers prefer a good quality pellet food, as these last fairly long and are also cheap, plus they contain most nutrients your oscar needs. Now, you ask, which pellet brand should i choose? Well, this is up to you. I prefer to use Hikari's Cichlid Gold, as this covers all essential nutrients, and it also contains Astaxanthin (more about that later). Remember to buy the right size pellet, too.

Of course, you can't just feed your oscar pellets 24/7, ya got to give him some treats (heatlhy ones, too). This is the rest of your oscar's diet. Remember, try and give your oscar the most varied diet possible. Here are some suggestions for you:

Shrimp: Available at your local market, shrimp are quick, yummy treats for most O's. Assuming your oscar is big enough, give him the hard tail part too. The tail is the best part, because it contains tons of astaxanthin- not only is this 'chemical' very healthy for your O, but it also brings out lots of red coloraton.

Naturally, oscars eat lots of crayfish, in fact this what much of their diet is made up of, and shrimp are an easily-available treat that just like what they get in the wild. If you can find some, real crayfish are great too (live ones included)

Fruits & Seeds: You can even feed your oscar some mixed fruit and even some seeds! In the wild oscars eat lots of fruit that falls from overhanging branches. Apples, cantaloupe and pineapple are all great.

Sprininula: Popular in the tablet form (do not confuse with 'algae' tablets). These also promote good coloration. Naturally, oscars feed heavily on Echinochloa polystachya, a semi-aquatic plant native to south-america and the southern us (plus mexico). Here's a quick pic:

Insects: If you can, pick up some crickets at your local pet shop. Keep them in a 'cricket keeper' and feed them some carrots or "cricket food", then toss them in your O's tank- O's love insects.

Earthworms: After a rain, go pick up some earthworms from the ground. Just don't 'harvest' from areas that have had decaying vegetation OR farmland- these worms could have harmful chemicals in them. Even better yet, pick some up at the bait shop.

Blood-worms: Freeze dried or frozen, these are a favorite of many O's. You don't have to thaw the frozen ones, just toss 'em in there.

Pick it up, toss it in. Squid, fish, you name it, oscars love it. (well most do, anyways)

Hikari Massivore: Large tablets used to feed predacious fish, make good treats for O's. Thanks cris for the idea.


Gold-fish/feeder: While it may be fun to watch your oscar snatch up an unsuspecting goldie, this is really not a good idea. Why? There's three reasons i can think of:

1) inhumane
2) thiamine- goldfish are high in this chemical, which breaks down vitamin b1- and essential nutrient your oscar needs.
3) diseases- "feeder goldfish" are often kept in extremely poor conditions and can easily pick up something bad. You can quarantine them, but you'll never know if they have an internal parasite, or something in the very early stages. I lost a baby tiger shovelnose catfish to internal parasites (baby tsn need to be feed live food until you can wean them on better choices).


On youtube you'll find several videos of mice-eating oscars. Oscars are not 'built' to eat mice, or anything else mammalian, for that matter.

The obvious:
If it sounds like a bad idea, it probably is. Don't waste your time.

Cat/dog food: For some annoying reason some people seem to think this it a good idea. It's not. Way too fatty for oscars.


Most oscars will eat until they die. There is a time to stop. When oscars are young, discontinue feeding when they're belly becomes rounded, or after about two minutes. When babies, about 35% of what oscars eat stays with them. Yeah, they grow fast.

You can feed you baby oscars two to three times a day, once they get larger (5-8'') you can slow it down to just once.

The time does not matter, but it is rather beneficial too feed each day at the same time, whatever time that may be. If you have a sucker fish (plecostomus) you may want to feed a nite, so he will get some food too, as they are nocturnal feeders.


If your oscar one day decides he won't eat, or just will eat a certain food, there are two things to do:

1) Just keep feeding, and hope he'll eventually come around. 90% (or more) of oscars do, they often just get bored or something, i dunno.

2) Add a couple drops of garlic juice to each pellet. This gives of a pungent smell that hopefully the oscar won't be able to resist.

If the above fail, biggamehunter came up with the idea to use ultrabite fish bait (general course fish type). this has a pheromone that triggers fish into a feeding frenzy..., just soak your pellets of whatever in it. more info here:


Unfortunately, if you slack with your maintenance, your oscar is likely to become ill. One the most common oscar illnesses is called Hole-in-the-head. Read on:


Photo of HITH infected fish

Hole in the head, or HITH (also known as HLLE- head and lateral line erosion) is an annoying common ailment in oscar fish, as well as many other cichlids. HITH 'creates' holes in the heads of larger cichlids. Why the head? Because HITH attacks the weakest spots- and sensory pits, small collections of tiny holes used to 'sense' stuff are located on the head. HITH also attacks the lateral line- a small series of indents that runs horizontally across both sides of the fish's body. (Because it is indented, lateral lines are weak spots, too) Once HITH has taken over these areas, it spreads, sometimes consuming the entire face of an oscar. However, most oscars die before this happens. Oh yah, HITH is fatal if not treated.

It is thought to be caused by the parasite Hexamita. However, Hexamita is a coldwater parasite that attacks the intestines of coldwater fish, and not cichlids. Studies done on cichlids with HITH show a percentage of 0 have Hexamita. Another contender is Spironucleus vortens, however tests done at the Vancouver aquarium on HITH infected fish demonstrate no signs of spironucleus. Some fish had it, others did not. A series of studies reveal that when discus and angel fish get HITH it is caused by Spironucleus, but when some other types of fish do it is NOT caused by spironucleus. Now, another flagellate known as Octomitus has been found in some HITH- infected fish. Both Spironucleus and Octomitus infect the gut of the fish (Hexamita does too, by the way), not the head or lateral line. So what causes the holes? Well, my guess is as good as yours. Somehow it is linked to these intestine-dwelling flagellates, I have no idea how, though.

Normally, a fish's immune system is strong enough to protect against HITH, but when a fish is stressed, the immune system is weakened and the fish succumbs to HITH. So, what causes the oscar to get stressed out in the first place? Well, there are hundreds of reasons, but there are four increasingly common ones that I will cover:

1) Poor Water Quality: This is the number 1 cause of HITH. If your nitrates are above 40ppm for extended periods of time and/or nitrites and ammonia are over 0. Fluctuations in pH and alkalinity can also cause stress as well.

2) Activated Carbon: Some fish in tanks with activated carbon get HITH, some do not. Why? Because it's not the activated carbon itself that causes the HITH, but the carbon dust. When carbon is transported, the particles rub together and cause the creation of 'carbon dust'. This can be removed by a thorough wash, but when people fail to do this, HITH often strikes up. But wait! That's not all, even if you wash your carbon well, you can still get HITH? Why? Because essential vitamins and nutrients present in the water are retained in the carbon, and this weakens the oscar. So really, just avoid carbon all together.

3) Poor Diet: An oscars diet is important. It needs to be varied, and should be based on a quality pellet. A good quality pellet is important, because generally they contain vitamins C & D, which when removed, can link to HITH.

4) Stray electrical current: It is important all your tank equipment is of good quality, because disfunction equipment could send out stray electrical currents causing stress to fish, and therefore causing HITH. Please not that this is just a theory proposed by some hobbyists, I myself have never seen it happen.

Have HITH and don't know how to cure it? Well first, make sure your fish indeed have HITH. The picture located above should help you.

Now, once you know your fish has HITH, do these steps:

1) Test your water. That means ammonia, nitrIte, and nitrAte and pH. If you don't have a test kit, buy one, or take a water sample to a local lfs- most will test for you for free. If your water turns out bad, do a 30% water change, and continue to do so daily. If your water tests fine (ideal parameters are ammonia: 0ppm, NitrIte: 0ppm, NitrAte: below 40ppm, pH: 6.5-8.5), do a water change anyways. Double check your water, too.

2) Remove all activated carbon, if you have any. Don't put it back in.

3) If your fish's diet is poor, make it better. That means 50-80% quality pellet food, and the rest 'goodies' of your choice. Optionally, add 'fish' vitamins to your fish's food (they should be available at a local lfs).

OPTIONAL: Add tsp of aquarium salt per 5 gallons of water, and/or turn temp up 80-82 degrees farenheight. If you increase temp, add an airstone too because the oxygen is more dissolved in warmer water.

If all else fails, you may need to use medication. The most common medication (in the US) is metronidazole. Jungle Hole-N'-Head guard and Octozin both contain metronidazole. Metronidazole kills the flagellate parasites that inhibit the intestine of the oscar fish.

Another common disease in oscars is called ick- it will basically look like someone sprinkled salt all over your oscar. Treatment is simple- turn the temperature up to about 84˚ farenheight. When you turn the temperature up add an airstone as oxygen is more dissolved in warmer water. Optionally you can also add 1 tsp of aquarium salt per 5 gallons of water. You can get ick medicene too, but make sure it has either methyln blue or copper as one of the active ingredients.


Well, the first step to breeding most any fish would be first getting a male and a female. Unfortunately, oscars are what we call "monomorphic" meaning the two sexes are externally indistinguishable. However, It is generally considered that males are more aggressive than the passive females, but this is not always the case. May people claim to have ways for sexing oscars, saying stuff like "males have longer fins" or "only males have occelations" but I have found most of this to be untrue. The only way that is accurate in the least is called venting. This is rather stressful to the fish, and cannot be done with accurate results until the fish is mature. This basically involves removing the fish from water and examining its reproductive organs. Males have an oo shape while females have an oO shape.

Since oscars are difficult to sex, and many pairs are not always compatible, you'll have to just buy several oscars and hope for the best. It is recommended you start with juveniles, and I am told the magic number is "6". Keep in mind that unless you have a very large facility you will probably be getting rid of some of those oscars as they mature.

Now, obviously your baby oscars will not start breeding right away. You'll have to wait until they are sexually mature. Unfortunately, there is no set time for how long this will take. It really depends on how much/what you are feeding, the size of the tank and the quality of water.

Once your oscars are sexually mature, you may notice that two of them will pair off. This means they will be swimming with each other, "tail-slapping", "lipping" and beginning the breeding rituals. They probably won't actually be breeding, but just going through a sort of "practice" round. Once you are sure that you have a pair, remove the other oscars and set the tank up for breeding. This means making sure the water is in it's maximum condition and that you have a flat piece of rock (e.g. slate) in the aquarium for them to lay their eggs on. You see, oscars lay a type of eggs that requires a hard surface for them to become situated. If you don't provide a flat piece of rock, they will probably just dig down in the substrate until they reach the glass and lay their eggs there.

Now that you have eggs, you will need to watch them very carefully. If the eggs remain white, it means they are either unfertilized or are infected by a fungus. If only some eggs are that way, you will want to remove these. Optionally, you can remove the eggs from the tank and place them in an aquarium with a dose of methylene blue, which will kill most fungus. However, you will not be able to observe the oscars taking part in the care and raising of their young.

Now, soon the eggs will hatch (assuming the oscars didn't eat them already, they can do this if it their first time around). What comes out is called "wrigglers" and they will not be able to much but wriggle. Luckily for you, they will have a yolk sac on them for several days and will not require feeding. After they have used up the yolk, you will need to feed them. At this stage, they will not be able to eat normal fish food, you'll have to feed them something much smaller. A great alternative is "brine shrimp" and you can buy or breed these on your own. After they have grown a bit, you can transfer on to crushed flake food, then normal flake food and so on.

Now keep in mind that sometimes the eggs may not hatch, especially in a new pair. As long as they weren't killed off by fungus or a hungry take-mate, you'll just have to wait and hope they get better at parenting next time! Keep in mind you may just have two females that are going over the rituals, and the eggs were never fertilized.

Well, I hope this article helped with your foray into oscar keeping! Have fun, and enjoy one of the coolest fish in the world!

Hole in the Head by Adam Dagna of World Cichlids
The Oscar - Astronotus ocellatus
Spironucleus - Hole In The Head, Head and Lateral Line Disease
Aquarium FD - Hole in the Head (Hexamita) - Disease Identification, Diagnosis & Treatment

1,148 Posts
A very nice well written article, Didnt check your spelling :) And dont think thats too important. Please contribute more

1 Posts
ok so i have 2 oscars that have already fertilize their eggs i believe! both parents are still surrounding the rock where the eggs are.. well i have arowana red devil 4 blood parrots and convicts..and they keep on trying to eat the eggs and i guess my oscar are getting really stress thats why they dont move away from the eggs.. do you the best way to save the eggs should be to move them in a seperate tank and add a dose of methylene blue.. or what can i do to keep the eggs save?
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