Fish size vs. Tank size

  • Get the NEW AquariaCentral iOS app --> http://itunes.apple.com/app/id1227181058 // Android version will be out soon!

OrionGirl

No freelancing!
Aug 14, 2001
14,053
342
143
Poconos
Real Name
Sheila
Trying to use native habitat size is ridiculous. For example, many fish are migratory, and may cover thousands of miles. Or, live in a lake, and visit different parts of the lake during different seasons and life stages. That doesn't mean that their needs can not be met within a tank, just that this is how they live in the wild. The opposite is true as well--bettas CAN survive in little tiny depressions that have barely 1/2 gallon of swimming area, but that doesn't mean 1/2 gallon of water in a jar is at all comparable. Rice paddies filter that water regularly, the jar can't.

Length is a tricky one, since it has several implications. the most common, though faulty, is that length directly correlates to waste production. No way! Heavy bodied fish may produce much more waste than a single long skinny fish (compare a 5 inch clown loach to a 5 inch weather loach--totally different body mass, totally different waste production.) Larger mass fish will produce more waste, no matter the length. Second component has to do with living space. Ideally, the fish should be able to comfortable turn around without banging into the sides of the tank. However, this does not mean that super flexible fish can be crammed into tiny tanks, nor does it mean that rope fish and the like require a tank 36 inches in all directions. Common sense should tell you if the fish is cramped in it's quarters.

Of course, activity levels of the fish matters a great deal. Frantic danios are not suited for tanks with little swimming room--they tend to 'carpet-surf' if kept in small hex tanks, for example. An adult pleco tends to be sedentary, so swimming room isn't as big a deal, though the pleco won't like sharing his turf with conspecifics.

Numbers matter as well--as with clown loaches, where one fish is often hidden and sedate, but a group is a rough-housing pack.

There is no magic formula, and the technical literature won't often help. Searching for people who have kept the same fish for at least half of it's natural life span, with it displaying normal behavior and size, is the best advice, IMO.
 

punch

AC Members
Mar 25, 2002
286
0
0
59
Petaluma, CA
You must take into account the adult size of the fish, as well as how fast it will grow. Get a common pleco at 2" and it will be happy in a 20 gallon tank but a few months down the line it will be cramped. When stocking my tank I tried to take into account
the adult size of my fish, not the juvanile size. Except with my clown loaches as they are slow growers, But I also relize I will have to get rid of them at some point (I'm not looking forward to that time) as my tank will not be of a good size and I can't afford a bigger one.
 

Mr.Jingles

It's Aqua Live!
Aug 26, 2000
217
0
0
MI, USA
maybe this can become a sticky? eh? put it in the archives or something? I think that maybe someone should look over these responses and validate them or back them up and add some input before it gets archived, if it does get archived.
 

yashinfan

AC Members
Jun 13, 2003
519
0
0
Well I think you're right in a way. My goldfish are probably 2" and 4" long, and my b/f has one that is a good 8" or more (it's HUGE!) Now, my fish when they are in the pond grow to the 4" size from the 2" when they were bought from the store. Obviously, if they were kept there they would not grow that large, and obviously my goldfish'll never be 10" because they live in a pond where they would be picked off if they were that large for half the year and an 8 gallon tank for the other half of the year. They aren't unhappy and don't get sick very often at all. So to me, I think that they do adapt their size to their environment.
 

Cloud-9

AC Members
May 11, 2003
216
0
0
Reidsville, GA
Visit site
Tank Size Recommendations

It's really hard to come up with a definitive answer as to how much tank you need for a particular fish. The easy answer, but certainly not the practical answer, would be to house the fish in the biggest tank that you can comfortably afford. In reality, we all have to find a balance. We have to balance the needs of the fish, our desire to keep that particular fish, and also the size of our budget.

A skilled and experienced aquarists can get by with a tank that is smaller than what most recommendations would say. Your frequency and consistency with regards to tank maintenance is also a very important consideration.

I do not like to see/read tank size recommendations from very uptight people who would always recommend a tank size that is certainly a very, very, very generous estimate. No, you do not need a 29 gallon tank just to keep one Firemouth! At the same time, I do not like to see/read recommendations from people who want to get by with as little as possible. I believe the answer is to find a reasonable balance. Do some research on the fish and take the following into consideration: budget and maintenance habits. In the end, find a balance and make a reasonable judgment.
 

OrionGirl

No freelancing!
Aug 14, 2001
14,053
342
143
Poconos
Real Name
Sheila
As requested above, I'm making this a sticky. It will stay a a sticky until it goes 30-45 days without an additional post, at which time I'll kick it over to Archives and add the link.

One more comment...Keep in mind that the above should notbe taken as the end-all guide to fish/tank selection. Instead, take this advice as a starting point for research and thought into what kind of fish you want, and what environment you want to provide them.
 

thom336

AC Members
Dec 17, 2002
651
0
0
Originally posted by yashinfan
Well I think you're right in a way. My goldfish are probably 2" and 4" long, and my b/f has one that is a good 8" or more (it's HUGE!) Now, my fish when they are in the pond grow to the 4" size from the 2" when they were bought from the store. Obviously, if they were kept there they would not grow that large, and obviously my goldfish'll never be 10" because they live in a pond where they would be picked off if they were that large for half the year and an 8 gallon tank for the other half of the year. They aren't unhappy and don't get sick very often at all. So to me, I think that they do adapt their size to their environment.
There is some research that shows that goldfish may be able to their size to the size of their enviroment. They apparently have these sensors which allow them to see how much space is aroud them. But this is of course controversal evidence, and Im not sure whether I agree with it or not - sounds a bit like something out of star trek to me. However, can I just add that even if it is true then it is still no excuse to keep goldfish in bowls.

And onto what oriongirl said about bettas. I would like to quote Julian Sprung on this, from a piece he recently wrote in Practical Fishkeeping magazine concerning small tanks:

"The increased popularity of the siamese fighter, Betta splendens, has promoted the development of various small containers. This may seem like cruel housing, but the aquarium has sufficient substrate and some plants. Bettas are accostomed to cramped quarters. After all, they naturally occur in shallow puddles and are quite able to tolerate fluctuations in temperature and water quality.
Putting some gravel or sand in the bowl offers substrate for biological filtration and a plant offers additional water purification. No aeration is needed since Betta breathe air by gulping it at the water surface."

But is this an excuse? Surely since we have the ability to provide the bettas with a higher standard of living we should? That goes for the goldfish as well - just because they can adapt to a smaller space, does it mean we should keep them in such small quarters? I think this takes us back to what was written by Cearbhaill about whether our fish thrive of just survive. I think as fishkeepers we have a duty to provide the highest possible standard of living for our fish, to ensure that they thrive, and maybe that means going one up on nature.
 

demon_surfer

MooOOoOOOoO
Jan 28, 2003
683
0
0
Visit site
i have read that alot of fish excret a chemcial into the water when they pee that limits growth, which i think is where the idea that they will stay the size of their tank came from. however if you do anything like a regular water change these chemicals will never build up enough to actually inhibit growth. im not 100% on this though so hopefully someone with more info can post...i believe i read abit about it on wetmans site but again..not sure lol
 

OrionGirl

No freelancing!
Aug 14, 2001
14,053
342
143
Poconos
Real Name
Sheila
Hormones will limit growth to a certain degree, and they are excreted all the time, so they certainly will build up to the point of inhibiting growth. Hormones break down fairly quickly (don't know an exact timeline, but within a few days is reasonable), but they still work on the basis of being constantly refreshed.

However--this is not to say that this is good for the fish. The same method would work to stunt humans, but that wouldn't be very ethical, would it? So why would it be ethical to deliberately maintain a fish in an environment that restricts normal development?
 
zoomed.com
hikariusa.com
aqaimports.com
Store