i've been seeing alot of posts lately in which people want to cram big fish in small tanks and when i'm suggestive of that being a poor idea, i've been told i'm wrong in more than a few cases. (i'm fairly new here so perhaps this issue has been ongoing for as long as AC has been here).
i'd like to take this opportunity to explain why cramming big fish into a too small tank is poor husbandry. fish load is much more than keeping ammonia levels down, oxygen levels high, pH stable and all the rest. it's more than having big filtration and changing lots of water. good husbandry is all about the fish, not the water. a variety of physiological, biological, metabolic and behavioural processes in fish are disrupted under crowded conditions. crowded conditions doesn't necessarily mean too many fish ... it can also be a too small tank for even a single fish.
just as you can tolerate being in a crowded car with the windows closed for awhile, fish can handle a crowded tank for awhile. but at some point it begins to negatively impact them in seriously harmful ways. we usually don't detect this until their immune systems are weakened and disease has taken hold. the problem is that by then, it's usually too late. fish maintained in tanks which are too small or in conditions which are too crowded, develop severe stress syndrome. these fish do not exhibit proper color, do not develop proper fin form, do not exhibit proper metabolic development, do not exhibit normal behaviour, do not develop proper musculature, do not develop properly functioning organ systems and as a result, slowly lose their inherant resistance to disease. this results in a significantly shortened lifespan and along the way, lots of diseases for which the poorly conditioned fish is a good target.
"hey, i kept a goldfish in a 5 gallon tank for 5 years and he was just fine". how many times have you heard that or similar. what these people don't understand is that the goldfish didn't die of old age. goldfish (and this is just an example) live for upwards of 20 years. having had one "survive" for 5 years is nothing to be proud of. arowana and Pacu are additional examples but there are plenty more. these fish grow to over 3 feet and need HUGE tanks. a 75 gallon tank is not huge. neither is a 150 gallon tank when it comes to such fish. experienced arowana keepers recommend aquariums with a footprint no smaller than 72x24 inches for 'mature' specimens and twice that for a fully grown fish.
you need to find out what the 'mature' size of a fish you're thinking of purchasing is going to be. if you don't have the proper tank size or don't plan on upgrading SOON (soon is not 3 years down the road), then don't buy the fish.
for some reason which i've never been able to understand, people treat fish in a manner they would never keep a dog or a cat. perhaps it's because you can't pet a fish and it doesn't sit in your lap. to me, ANY animal which you 'adopt' becomes a responsibility which dictates that you maintain it in a way that maximizes it's health and 'happiness'. that it lives to it's genetically predetermined age, that it remains healthy and that it lives in an environment which allows it to behave in a normal, stress free way. i don't understand why you'd keep a fish at all if you're not going to provide optimum conditions for it. there are so many fish out there to choose from ... why not pick those that you CAN provide a proper home for rather than going for that macho predatious fish and small dog eating machine just because it strikes you as "cool".
what is normal behaviour anyway? the interraction of a mixed community tank and/or the behaviour of a single species is one of the single most important factors to consider when selecting fish for your tank. you want the fish you're keeping to have the ability to exhibit "normal" and functional behaviour. abnormal behaviour results in stress. stress leads to disease. disease can lead to death. for example:
1. if species (A) does not get along with (is incompatible with) species (B), then these fish don't belong in the same tank no matter how few fish you have or how large the tank. "getting along" is based on the visual and behavioural Q's that each fish species is genetically programmed with. this is why African cichlids generally don't belong in the same tank with Central American cichlids. Africans don't "understand" Central American fish speak and this leads to behavioural problems and stress.
2. if species (A) has specific food or water chemistry requirements which are completely different from species (B), then these fish don't belong in the same tank no matter how large the tank is.
3. if species (A) is aggressive and defends a territory of 2 square feet, then you cannot expect to successfully keep more than one of these fish in a tank which is smaller than 2 square feet. convict cichlids are an excellent example of this ... this little fish aggressively defends territories of about two square feet give or take. if you have a tank which allows only that much room and no more, the convict will defend the entire tank to the detriment of any other fish (no matter how large it is) in that tank.
fish need room to swim without having the rest of the tanks inhabitants "in their face" continuously. think about your local lake or river --- the fish are free to inhabit whatever space suits them biologically. if it gets crowded by their standards, some will disperse and move to other areas where they again have the space they need to exhibit functional behaviour.
it's difficult to allow for that "space" in your tank -- the fish have no escape within the confines of your tank so it's up to you to insure that the fish have that space in the first place. if your tank "looks bare" .. it's probably just right.
i'd like to take this opportunity to explain why cramming big fish into a too small tank is poor husbandry. fish load is much more than keeping ammonia levels down, oxygen levels high, pH stable and all the rest. it's more than having big filtration and changing lots of water. good husbandry is all about the fish, not the water. a variety of physiological, biological, metabolic and behavioural processes in fish are disrupted under crowded conditions. crowded conditions doesn't necessarily mean too many fish ... it can also be a too small tank for even a single fish.
just as you can tolerate being in a crowded car with the windows closed for awhile, fish can handle a crowded tank for awhile. but at some point it begins to negatively impact them in seriously harmful ways. we usually don't detect this until their immune systems are weakened and disease has taken hold. the problem is that by then, it's usually too late. fish maintained in tanks which are too small or in conditions which are too crowded, develop severe stress syndrome. these fish do not exhibit proper color, do not develop proper fin form, do not exhibit proper metabolic development, do not exhibit normal behaviour, do not develop proper musculature, do not develop properly functioning organ systems and as a result, slowly lose their inherant resistance to disease. this results in a significantly shortened lifespan and along the way, lots of diseases for which the poorly conditioned fish is a good target.
"hey, i kept a goldfish in a 5 gallon tank for 5 years and he was just fine". how many times have you heard that or similar. what these people don't understand is that the goldfish didn't die of old age. goldfish (and this is just an example) live for upwards of 20 years. having had one "survive" for 5 years is nothing to be proud of. arowana and Pacu are additional examples but there are plenty more. these fish grow to over 3 feet and need HUGE tanks. a 75 gallon tank is not huge. neither is a 150 gallon tank when it comes to such fish. experienced arowana keepers recommend aquariums with a footprint no smaller than 72x24 inches for 'mature' specimens and twice that for a fully grown fish.
you need to find out what the 'mature' size of a fish you're thinking of purchasing is going to be. if you don't have the proper tank size or don't plan on upgrading SOON (soon is not 3 years down the road), then don't buy the fish.
for some reason which i've never been able to understand, people treat fish in a manner they would never keep a dog or a cat. perhaps it's because you can't pet a fish and it doesn't sit in your lap. to me, ANY animal which you 'adopt' becomes a responsibility which dictates that you maintain it in a way that maximizes it's health and 'happiness'. that it lives to it's genetically predetermined age, that it remains healthy and that it lives in an environment which allows it to behave in a normal, stress free way. i don't understand why you'd keep a fish at all if you're not going to provide optimum conditions for it. there are so many fish out there to choose from ... why not pick those that you CAN provide a proper home for rather than going for that macho predatious fish and small dog eating machine just because it strikes you as "cool".
what is normal behaviour anyway? the interraction of a mixed community tank and/or the behaviour of a single species is one of the single most important factors to consider when selecting fish for your tank. you want the fish you're keeping to have the ability to exhibit "normal" and functional behaviour. abnormal behaviour results in stress. stress leads to disease. disease can lead to death. for example:
1. if species (A) does not get along with (is incompatible with) species (B), then these fish don't belong in the same tank no matter how few fish you have or how large the tank. "getting along" is based on the visual and behavioural Q's that each fish species is genetically programmed with. this is why African cichlids generally don't belong in the same tank with Central American cichlids. Africans don't "understand" Central American fish speak and this leads to behavioural problems and stress.
2. if species (A) has specific food or water chemistry requirements which are completely different from species (B), then these fish don't belong in the same tank no matter how large the tank is.
3. if species (A) is aggressive and defends a territory of 2 square feet, then you cannot expect to successfully keep more than one of these fish in a tank which is smaller than 2 square feet. convict cichlids are an excellent example of this ... this little fish aggressively defends territories of about two square feet give or take. if you have a tank which allows only that much room and no more, the convict will defend the entire tank to the detriment of any other fish (no matter how large it is) in that tank.
fish need room to swim without having the rest of the tanks inhabitants "in their face" continuously. think about your local lake or river --- the fish are free to inhabit whatever space suits them biologically. if it gets crowded by their standards, some will disperse and move to other areas where they again have the space they need to exhibit functional behaviour.
it's difficult to allow for that "space" in your tank -- the fish have no escape within the confines of your tank so it's up to you to insure that the fish have that space in the first place. if your tank "looks bare" .. it's probably just right.
Last edited: