The prisons we keep

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plebian

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I don’t think most people give it a thought, but an aquarium is at best a form of gilded cage. Some poorly kept aquariums are more like a Turkish prison, overcrowded and polluted. Overcrowding is the rule, even among better kept aquariums.

The old “one gallon per inch of fish” rule is wholly inadequate for all but the smallest fish. As far as maintaining water quality, the mass of a fish is more important than its length. Assuming adequate water quality, the length of the aquarium, not the fish, should then take precedence.

There are very few species that don’t spend most of their time swimming, and even the smallest species benefit from longer aquariums. Water depth is simply not very important except perhaps for some of the larger species, which probably shouldn’t be kept in any hobbyist aquarium to begin with.

It is my personal opinion that nobody should be keeping any fish, no matter how small, in an aquarium less than 36 inches long. There are exceptions, like Betta splendens, but they are few. Even smaller tetras, like neons, appreciate swimming space. Smaller fish are typically found in schools, or shoals, as a means of avoiding predation. They are always more comfortable in groups, the smaller the fish the larger the group. The larger the group, the longer the aquarium.

For example, I currently have 9 cardinal tetras in my 180 gallon aquarium. Except when actively feeding, their group typically occupies a volume of water roughly measuring 12”H x 18”W by 24”L in the middle of the water column. That’s equivalent to 22 gallons of water.

Since you cannot fill a tank to the top with water, and since you would need some substrate and some plants and/or driftwood for shelter, you would need a 29 gallon tank to provide an minimum optimal volume of water. But a 29 gallon tank would not meet the horizontal space requirements of a group of 9 tetras, since it’s only 12” wide. The smallest standard size tank that would accommodate an optimal swimming space for a group of 9 cardinal tetras is a 40 gallon breeder.

Most hobbyist resources recommend minimum acceptable aquarium sizes for any given species. While it is possible to maintain healthy fish according to these recommendations, it seems the word “minimum” is frequently overlooked. Minimum conditions should not be interpreted as optimal.

Aside from requiring increased maintenance, smaller aquariums frequently have a negative effect on species behavior. This is especially true of community aquariums. Most species do not naturally mingle with other species. Each needs their own space to be comfortable. In fact, even members of a single species require what might be called their personal space. This is obvious among territorial species, but even shoaling species require personal space.

In the example I gave above for a small group of 9 cardinal tetras, each fish typically maintains a distance from its nearest neighbor of from 4” to 6”. That distance shrinks when other, larger species are nearby. This is what is referred to as schooling behavior. It is a defense mechanism used to avoid predation.

Very few species form schools unless threatened. Instead, they spend most of their time congregating in loose groups referred to as shoals. While schooling behavior is highly valued by most hobbyists, in most cases schooling behavior is an indicator of stress. Brief episodes of schooling are perfectly normal and healthy among shoaling species. But frequent occurrences are an indicator of unusual levels of stress and something to be avoided.

Like many, when I was young my parents purchased a small (10 gallon) aquarium and overstocked it with swordtails, mollies and guppies as a form of entertainment. The aquarium had no filtration, only an airstone and the substrate consisted of colored marbles. Needless to say, the fish did not survive long.

The first aquarium I purchased as an adult was a 30 gallon equipped with an undergravel filter. Initially, I kept a few goldfish. That was before I learned how large goldfish could become. I replaced my 30 gallon with a 55 gallon which I later populated with 4 adult discus. At the time, and even to this day, most discus keepers will tell you that’s perfectly acceptable.

Even though I had relatively little knowledge at the time, as I observed the behavior of my fish I realized that a larger aquarium was necessary. I told myself then that if I ever owned another aquarium it would be at least 125 gallons.

Now, many years later, I have a 180 gallon aquarium. I designed and built it myself with the goal of maximizing swimming space. Unlike a traditional 180 gallon aquarium which provides 6 linear feet of swimming space, my custom built aquarium provides 9 linear feet of swimming space.

My aquarium currently houses 5 discus, 9 cardinal tetras, 4 emerald Corydoras, one dwarf spotted catfish, one bristlenose catfish, and one red lizard catfish. I consider this very close to a maximum optimal stocking level.
 
My aquarium currently houses 5 discus, 9 cardinal tetras, 4 emerald Corydoras, one dwarf spotted catfish, one bristlenose catfish, and one red lizard catfish. I consider this very close to a maximum optimal stocking level.

While I agree with most of what you’ve said, I would say your groups are far too small to be close to “optimal”. Keep, say, 30-40 Cardinals and they’ll shoal a lot tighter than 4-6” apart. These three shoaling species naturally live in groups a lot bigger than 4,5 and 9 individuals. Increase the numbers and their behaviour will be more natural.

I disagree with your exception to the minimum tank size rule. Betta splendens males will roam over a whole paddy field in nature. There’s no reason why it is more suited to a small tank than other fish.
 
While I agree with most of what you’ve said, I would say your groups are far too small to be close to “optimal”. Keep, say, 30-40 Cardinals and they’ll shoal a lot tighter than 4-6” apart. These three shoaling species naturally live in groups a lot bigger than 4,5 and 9 individuals. Increase the numbers and their behaviour will be more natural.

I disagree with your exception to the minimum tank size rule. Betta splendens males will roam over a whole paddy field in nature. There’s no reason why it is more suited to a small tank than other fish.
Betta's actually have about a 3-square-foot territory (depending on the water depth, which is a lot more than a few gallons), but other than that, I agree with you.
 
Betta's actually have about a 3-square-foot territory (depending on the water depth, which is a lot more than a few gallons), but other than that, I agree with you.

They’re only territorial if they need to be, and a square meter is a big enough territory. The only reason to be territorial outside of the breeding season is high population density. They’ll defend a feeding territory if they have to but otherwise a lone male will wander over quite a large area. You can easily see this by putting one in a large tank. It will use the whole of the tank.
 
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They’re only territorial if they need to be, and a square meter is a big enough territory. The only reason to be territorial outside of the breeding season is high population density. They’ll defend a feeding territory if they have to but otherwise a lone male will wander over quite a large area. You can easily see this by putting one in a large tank. It will use the whole of the tank.
I agree that they will naturally roam a very large area, but not an entire patty field.
 
Its definitely an ethical grey area for me... I do struggle with it especially when you get into the details of how the trade operates and how the fish actually get to us. The impact of how we keep them weighs heavy too - your approach is truly commendable with so few fish in such a big tank and the benefits of it but there is definitely questions over if you actually have enough fish for them to be thriving - some members here have shared papers about the stress and general health levels of schooling and shoaling fish when kept in low numbers and its quite startling, I understand your space requirements but getting to 20 Cardinals and 12 Emerald Cats wouldnt hurt?

I think the other thing to remember is that when we started our tanks we didnt really appreciate a lot of whats been discussed here and it takes a long time for it to really sink in - I know for me it was years before the buzz of just having fish and having a collection passed and I started to understand whats involved. I suppose the true ethical question is - would you choose to keep fish when you first started if you knew everything you know now? I'm not sure I would...
 
I certainly support large groups of complementary fish. My signature tank is 200l. In it are approximately:
60 cardinals
30 cories (mostly paleatus but I do have a few sterbai)
20 pencilfish (nannostomus marginatus)
I do not feel the need to have a variety or a so called centrepiece.
At no time does the tank ever look overcrowded, or anything but calm and relaxed, unless I drop in a single algae wafer when all the cories descend on it at once, but they would do the same in a tank 20 times the size ;)
 
There are very few hard and fast rules or universals when it comes to keeping fish inaquariums. One would be, put the into water.

But, fish in a tank are not living in a wild environment. Lets talk about Cardinal Tetras. How do these fish spawn? They are egg scatterers. Why is this the case as opposed to the being pair bonded, cave spawners, bubble nest builders etc. etc.? The answer is simple. Nature needs to have them make a tome of eggs as many will be eaten.Then there ones that htchout produce what most other inhabitants in their areas see as food. And even those that make it to adulthood still have to worry about being on the menu. So nature came up with schooling as a defense mechanism.

Now put a dozen of such tetras into a 20 gallon tank., Put in some plants keep the water clean and feed them properly and they will likley lall live longer lives than they might have in the wild. Yes, ideally they should be in a bit larger tank but they are not going to suffer being eaten alive. And the way you know that is the most likely will not school. They may bunch but they will also meander.

Or how about bare bottom tanks with no plants? I kept a breeding colony of 13 zebra plecos in such a tank for many years. They spawned like crazy and I got many babies. They are now in another tank with a sand substrate but they rarely spawn at their advanced age.

No, in nature what happens to a fish that gets a bacterial infection compared to when this happens in one of our tanks. If we are responsible fish keepers, we will try to treat the fish going as far as to use antibiotics. I do not think there is such a thing as a doctor fish. (There are nurse sharks but they eat fish rather than carinf for them when they are ill.)

And then there is one big question. What is that fish do all day and night besides living, eating sleeping and reproducing. The best answer is they become a part of the food chain and some will make it to die of old age.

Finally, a lot of the fish we buy are not taken from the wild, they are farmed for us to put into out tanks. They might not even exist if not for this. More than likely that have lived in heay stocking from birth. Our tanks may be like freedom to some of these fish?

I understand about trying to match the tanks we put our fish into to be as much like nature as possible and to be roomy. But that is less important, imo, than providing many of the other benefits that the fish would not have if they lived in the wild.

It is the responsibility of every fish keeper to provide as much as they can to benefit the fish. I would not keep a school of tetras in a tank with their cousins, piranah. I do not have birds circling my tanks hoping the nab a fish lunch. I do not have polution from mining and other industries flowing into my tanks. So excuse me if I did not provide quite as much room as they might get in the wild, I made almost every aspect of their lives better than they would have in the wild.

There is a difference between put fish into a tank which is less than the optimal size, that is not the saem thing as putting them into really small spaces relative to their needs. Lets not forget how aggressive Rift Lake fish in tanks are deterred from picking on the weaker ones- over stocking. I try not to do that with my territorial plecos. ;)

Lets get realistic. There are people out there who are cruel to animals like dogs, cats horses etc. When people like that keep fish, they will nit treat them any better than to do other animals. Hopefully, such people are not a large part of the population.
 
I don’t think most people give it a thought, but an aquarium is at best a form of gilded cage. Some poorly kept aquariums are more like a Turkish prison, overcrowded and polluted. Overcrowding is the rule, even among better kept aquariums.
Agree, but fish (most fish) are not really sentient creatures, they aren't able to understand they are in prisons. If the water parameters are good (which means no overcrowding) then it's ethically fine. Some fish require more space and numbers because they swim a lot, or because they are shoaling fishes, or some require strong current, some almost no current.. these are the things to respect.

My aquarium currently houses 5 discus, 9 cardinal tetras, 4 emerald Corydoras, one dwarf spotted catfish, one bristlenose catfish, and one red lizard catfish. I consider this very close to a maximum optimal stocking level.

Yet if you take out those 5 discuses, you could have put in 80 tetras and 10 corys (20 tetras/10 corys per each discus you remove) based on how much a discus eat. Then they'd school in appropriate number.
 
Basically, every cage, kennel, tank or whatever home in captivity is too small in comparison to living freely in the wild. That's a fact... But this is an argument that will never have a good answer. But we make the best of it while taking care of our pets.
 
@plebian

I consider your tank to be under stocked. I had 65 cardinal tetras in a 75 gal, and they did fine. Incidentally. I had one cardinal get sick and it was unable to stay upright. So it swam upside down. I could spot it easily in the group of 75 as its colors were reverse- red on top and blue on the bottom. My mistake was the tank also held 6 assorted size clown loaches and a numbers of SAEs (I mixed SA and Asian). The tetras almost always schooled either in one large group but now and then they would break into two groups. They did not take long to become one again. Those clowns started in smaller quarters got moved to the 75 and are now in a 150. I recently lost my oldest and biggest clown. My best estimate was that it was about 24 years old and almost 12 inches TL. I was given it as a gift (with three more) when it was close to 4 inches. I had it for 21+ years.

I have a zebra pleco that is at least 21. He has lived only with other zebras his entire life. When I got it, along with 12 others in a breeding group, they went into a 30 gal. breeder. They gave me about 500 babies over the years. He was recently move to a 40L with about 20 other zebras. That tank is 48 x 12 inches or 4 sq. ft. The 30B is 36 x 18 inches and that is 4.5 sq. ft. His first tank was roomier for a fish which is somewhat territorial. Plecos generally need area more than length or volume.

Like I said, there are very few universal rules in fish keeping.

And most dogs would rather live with humans in an apartment than to have to survive in the wild. A fish in the wild has to work to find food and may not do so every day. A good pet keeper feeds his or her dog every day. If they get sich they usually go a to vet. No vets roaming the wild looking for sick dogs to help.

I have always told folks that I believe that fish have only three thoughts that motivate their behavior:
1. Can it eat me? (Waiting to answer that may mean it gets the answer in the stomach of another fish.)
2. Can I eat it? (I will try.)
3. Can I spawn with it. (I will try.)
But then I am not a icthycologist, nor do I speak fish or read fish minds.
(Icthycologist- a psychologist for fish.)
 
I disagree with your exception to the minimum tank size rule. Betta splendens males will roam over a whole paddy field in nature. There’s no reason why it is more suited to a small tank than other fish.
In the wild, Bettas live in an optimal density of 1.7 fish per square meter, or roughly one fish per half square meter. Contrary to someone who stated they move throughout rice paddies, they never leave the small territory they occupy unless they cannot defend it or there is a lack of sufficient food. That's far greater density than is optimal for discus, or even tetras. It is also worth noting that the Bettas most people are keeping are long-finned and less mobile than wild caught Bettas.

"Evolution, Culture and Care for Betta Splendens, University of Florida publication"
 
While I agree with most of what you’ve said, I would say your groups are far too small to be close to “optimal”. Keep, say, 30-40 Cardinals and they’ll shoal a lot tighter than 4-6” apart.
My group of cardinals originally numbered 30. I observed no difference in behavior whatsoever. The larger the group, the larger the space they occupied. It's why I removed more than half of them.
 
Agree, but fish (most fish) are not really sentient creatures, they aren't able to understand they are in prisons.
I wouldn't jump to that conclusion. Fish are very much aware of their surroundings. My discus will watch me from 5 meters away. Gold fish were taught to "drive" a mobilized aquarium to specific locations within a room.

When I lived in Seattle, there was an octopus at the local sea aquarium that would climb out of its tank at night, crawl across the floor, climb into a another tank, eat one of the fish in that tank, then return to its own tank afterwards. This went on for days, and the keepers at the aquarium couldn't understand why fish kept disappearing. It wasn't until they installed cameras that they discovered what was happening.
 

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