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Main Index > Detailed Fish Profiles > The Tetras > Penguin Fish
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This page will give a completely detailed profile of the selected fish, from A to Z. The profiled fish will be chosen randomly by Badman, and will come from the complete genre of tropical fish. New profiles are added on a regular basis. If you would like to submit a profile for the site please contact me. Don't forget to let us know you experiences with this fish by filling out the

South America



Thayeria boehlkei


    Another of the old time favorites, the Penguin fish has a look all its own. A peaceful and undemanding fish that makes a great addition to any community aquarium.

Quick stats:

    Listed tank sizes are the minimum
    Size: Up to 2 1/2 inches (8 cm)
    Tank: 24 inches
    Strata: Top, middle
    PH: 5.5 to 7.0
    Hardness: Soft to hard dh range 4-20
    Temperature: 73° to 82° F (22-28°C)


    Order: Cypriniformes
    Suborder: Characoidei
    Family: Characidae
    Genera: Thayeria

Common name:

    Penguin Fish

Image gallery:
    Additional species photographs


    Badmans' Forum


    Peru and Western Brazil, the Amazon basin.

General Body Form:
    A rather long fish with much lateral compression. The upper and lower profiles are very similar in appearance. The bottom of the rear fin (Caudal) is slightly longer, giving the penguin its one of a kind look.

    A Black longitudinal stripe starts at the end of the gill cover plate and runs all the way to the base of the Caudal fin where it turns downward to the bottom tip of the tail fin. A shinny Gold colored line runs on either side of the thicker Black stripe. The upper main body color is a gold or bronze color and the lower body is a silver to gray color. The fins are clear with a slight Yellow tint and the front of the Anal fin has a milky front.

    An easily cared for fish the penguin is omnivorous accepting flake, frozen and live food. The addition of some vegetable matter in the food is beneficial. They are adaptable to a wide range of water conditions, although it has been said that they are sensitive to high Nitrate levels. The tank should be loosely planted with plenty of open space for swimming. They swim at an angle facing up and are a schooling fish and should be kept in groups of at least six. An all around winner for the community aquarium.

    Found in slow moving waters of the Amazon basin, among scattered patches of plants.

    A very prolific breeder often having broods of over 1000, a fairly large breeding tank is needed. The water should be soft and on the acidic side (5.5). The substrate should consist of fine leafed plants to catch the large number of eggs. Females when ready to spawn have a very distended belly due to the large number of eggs. After spawning the pair should be removed and a portion of the water should be changed due to the large amount of sperm released by the male which could foul the water. The eggs hatch in less than a day and the fry are very small and need to be fed the smallest of foods available.

Your comments:


Please remember that the following comments are personal experiences and may or may not apply to your setup. Use them as guide to help better understand your fish, like us all individuals will behave differently under different circumstances.


From: Patty
This fish is not necessarily an aggressive fish. Be careful what you mix. Check compatibility charts and be careful when introducing new fish. Tetras, guppies, and danios do not usually get along that well. I have angels, gouramis, and tetras, we have no aggression problems. Also, make sure the fish tank is not crowded. One inch per gallon is a general rule of thumb for fish. Overcrowding will cause aggression in even the most docile fish.
From: Chris
Did have 5 penguin tetras because, like other posters, they look beautiful together. I recently moved the tank around a bit, replacing a couple of decorations/ornaments and moved some plants around as they're growing quickly. I expected the fish would need a bit of time to adapt to their 'new' surroundings but I was not expecting them to hide separately in the plants or to start attacking each other and the other tetras. During the day, we lost one of the larger penguin tetras so immediate change was necessary. They're in a 72 litre tank with 3 silver tip tetras (we did have 4) and they all started fighting one another. On reading here, I discovered that I'd spread the plants out too much, and taken away their room to swim, hence the major territorial issues. I've literally just spread the plants round the edge of the tank, as advised here, and immediately they're schooling again and getting on with the silver tips. I've also slightly increased the water flow in the tank as it's also noted below, and I've seen myself, that they like to swim into the stream. are perhaps kept in check by the presence of the larger fish?
From: Simon
I have 10 of these in a 450 litre community tank. They are very active and like swimming "upstream" in the filter outflow - very entertaining. They school well, and interact a little with my 30 Emerald Eye Rasboras, but no aggression. I have 5 Red Line Torpedo Barbs, so the penguins are perhaps kept in check by the presence of the larger fish?
From: Jan Altink
Going through the earlier comments I find it striking that the people complaining about the apparent aggressive behaviour of this little fish always seem to miss the fact that they are keeping a schooling fish in numbers of 2, 3 or 4. These small numbers do not make a school and the fishes are therefore most likely prone to showing stress behavior. One species does this by hiding, another species may turn (a bit) aggressive. I have seen this many times and mostly when people tell me they have these sort of problems with a certain species it's because they are not keeping them in sufficient numbers. Instead of giving 3 out of 4 away, a better solution would be to get 4 more. In my opinion, any schooling fish should be kept in a group of 10 or more. This way the fishes all feel secure and have enough of their kind around to keep themselves busy with things like a (food) hierarchy, should they have a need for it (such as Tiger barbs). I've been keeping and breeding tropical fish for over 35 years now and at the moment I've got some 50 aquariums housing mostly tetras, danios and gouramis. Among them is a group of Penguins (15) who live together with White Clouds, Gold tetras, Lemon tetras and some Swordtails. Never seen agression of any kind.
From: Lloyd Pollock
Another thumbs down in my case. although I had already done a little research on here about this fish, I still fell for its charming looks. I had 6 cardinals & 5 glow lights but since this species (4) was introduced I noticed it bullying the other fish chasing them around nipping their fins. My stock reduced to 2 Cardinals & 3 glow lights. Yesterday I added 3 harlequin tetras & 3 rummynose & had to fish out a dead harlequin this morning! I have just gave 3 away to a neighbour so now I have 1 left, ill check his behaviour & if things don't improve ... he will be joining the rest. I understand that different Penguin tetras have different personalities but it should be noted that this species is not 100% friendly.
From: Kitt
I have a few penguin tetras and I can get them to breed whenever I want. The trick is to add sudden rushing water to your tank via a pump system. I discovered this by unclogging my pump which prompted spawning twice. Now if I turn the water pump off for a few days and then turn it on again, the fish again spawn. Rushing water must simulate some behavior of the species in the wild like moving up a small tributary with rapid current, etc.
From: Bruce
I have 6 of them at the moment due to my preference of not overcrowding a modest tank, and I must say they are quite peaceful fish, very pleasant and easy caring. They socialize well with white cloud mountain minnows and have done the same with Zebra Danio's. The only time I get any aggressive behaviour from them is when one of them passes away, and the spot is either waiting to be filled or is filled by another replacement, as the feeding Hierarchy is effectively screwed up, as normally the largest (and poss. eldest) one out the batch is normally the one that passes away, throwing the chain into dispute, however, after a few weeks, I have found that its not normally too bad. I would recommend these fish over tetra species, due to their strong resistance to Illness and the ability to not be bullied (or eaten) by another species.
From: Kevin
When you see a tank of these fish at your local shop they are the most idyllic schooling fish. But not so at home with only a few (I have 6) They ignore other fish and there seems to be a constant power struggle. With one dominating and chasing the other Penguins. I have 2 tanks and moved these fish about but it's always the same. I would recommend Rummy Nose Tetras as the BEST schooling peaceful fish. Pentazona Barbs are peaceful too.
From: Kana
I have a 20 gallon tank with 4 penguins, 2 corys, 3 black skirt tetras, and some neon and glowlight tetras. The penguins are the most peaceful of all my fish, and the rest are very peaceful also. I cannot understand why a penguin fish would be aggressive toward other fish, except for the fact that they do not have enough room. I have seen the most placid, peaceful fish be aggressive and territorial if there is not enough territory to go around. I have kept fish for a long time, and I think that the cramped areas are the thing that make fish most aggressive.
From: Sissy
I have a school of six Penguin Tetras in my 55 gallon community tank. They share the space with many other tetras including harlequins, neons, cardinals, lemons, and black neons. There are many others including a Beta, guppies, and a school of marble hatchets. They all live peacefully together and I have never once seen them act aggressively towards any of my other fish.
From: Danielle
I have a community tank containing 6 penguin tetras, 2 opaline gourami, 2 mollies, 2 clown loach and 1 lone neon tetra. The penguin tetra are really nice fish to watch and although mine do not school they are peaceful fish and I haven't had any problems with aggression towards the neon tetra. I love these fish and will be adding another 6 soon to see if they will school in a larger group.
From: Laurent
I am very surprised with all the comments below! I have 16 tetra penguin in my tank along with guppies, cherry and amano shrimps and a couple of colisa lalia. I have them for 6 months now and despite they are very active they also are very peaceful with all their tankmates. They do not even eat the baby guppies!
From: Eric Olson
I have to agree with the other comments on this species. For my first aquarium (10 gallon) I purchased 3 Cory Cats and 6 Penguin Tetras. At first everything was fine, but within a week each of the Penguin Tetras had established its own territory in the tank. The only time they would move around the tank would be to fight with one another or to feed; otherwise they would stay in the same position all day. They did leave the Corys alone, but I don't enjoy watching fish fight, and the tank was probably too small for that many Penguins anyway (my mistake), so I returned them to a local fish store where they are now in a large display tank where they are schooling nicely, probably because they are no longer the big fish in the little tank and they have bigger fish to worry about now.
From: Peter Wignell
I put 3 penguin tetras in my tank a week ago. Other species in the tank are harlequin rasboras, cardinal tetras, black stripe tetras, yamato shrimp and 1 catfish. I only put in 3 penguin tetras. The schools of other fish all outnumber them. The day after I put the penguin tetras in the tank one of my harlequins was missing half its tail and subsequently died. Apart from that there hasn't been any other trouble. The penguins appear to have staked out a small area of the tank as theirs and chase other fish away but they aren't overly aggressive.
From: Alvin Song
Penguin Fish are only peaceful among fishes larger than them. Totally unsuitable for community tanks with small tetras. In my planted tank, a school of 10 Penguin Fish has became extremely Aggressive towards other fish species: my white cloud mountain minnows, harlequin, badis badis, and even zebra danios. My recommendation is to have Penguin Fish with catfish species, snails, shrimps only. I find the description of Penguin Fish "peaceful in community tanks" absolutely hilarious.
From: Graham Chalker
I have found the same with Penguin Tetras they can become very tank dominant and become aggressive towards other fish that swim in their water level. I have lost up to 12 small Guppies in the last month due to the Penguin Tetras so I will be passing them back to the shop. They seem to behave more when there is a larger more dominant fish in the tank i.e. an Indian Gourami or lace Gourami. I do not recommend these fish for community tanks with small fish.
From: Julie
I have an 80 gallon tank, and in it I have about 14 cardinal tetras, 4 serpae tetras, 3 swordtails, 2 blue Moscow fancy guppies...and a few bottom feeders. We just introduced 6 penguin tetras today and I am not at all pleased. They're picking on my guppies like you wouldn't believe, and nipping at the fins of my serpaes (which are my favorites in the tank). I'm seriously considering taking them back to the pet store. They're not docile, nor are they peaceful. I'm shocked---I thought mainly all tetras were great community fish. These aren't. =( Take caution when buying these for your community tank, they seem to like long fins!
From: Donna E.
I have found these fish to one of the more aggressive fish I have had. I had 5 in my tank, and they chased each other and their tank mates around constantly! One of the worst assaults was the removal of one male's entire tail fin. He survived for about 8-9 months, but it was only because he was able to hide in one of the plants. They all have missing scales and missing bits of tail and fins, and they killed 2 Honey Gouramis shortly after I introduced them to the tank. Nope, I would not purchase them again, even though they are quite beautiful.
From: Lord Heath
Unfortunately, my experience with these fish has been largely negative. I have just had to get rid of mine because I find them aggressive towards other fish. They appear to chase other species of fish around the tank and yesterday I found 3 dead fish (1 zebra danio, 2 swordtails) and attribute the deaths to the Penguins. So naturally, I found your "peaceful" fish quite contrary to my own findings.
From: Adrian
Penguin tetras are a peaceful and undemanding fish. They are best kept in a group as they are a shoaling fish. I have two pairs and they are happy with four pairs of tiger barbs and a pair of ghost. They eat all types of dried foods.
From: Joe
These fish are one of my favorite tetras. They have nice colors, and a nice body form. The penguin tetra also love to just "hang out". I have 5 of them with some other tetras in a 45 gallon tank, and they love to just float in front of the glass. I have never seen these fish fight with other fish in the tank, but they would probably be attacked a lot if they are kept with more aggressive fish. I recommend these fish to people who are new at fish keeping, because the penguin tetra isn't demanding on when it eats, or what the water is like (just as long at the temp. is good and not too dirty).





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