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Fish size vs. Tank size

Discussion in 'Freshwater Archives' started by vaheelsfan, Jun 4, 2003.

  1. vaheelsfan

    vaheelsfan AC Members

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    I have a question about all of these mimimum size requirements that people always talk about. Don't fish usually grow to the size that their environment allows them? I understand that you can't keep a 6" fish in a 10 gallon aquarium. BUT, just because a fish can reach a size of 12" doesn't mean it has to to be healthy. In the wild, fish grow to the size their environment allows them to. This is why in some places a fish of 12" would be a large specimen, but in another place, the same species would have to be 30" to be considered large. Like I said, I know that there is a point where the environment is just too small, but I also don't see where a fish would have to be allowed to reach it's maximum size for it to be healthy and or happy. Is my line of thought way off base here, or does it make sense or is it somewhere in between?
     
  2. mogurnda

    mogurnda vaguely present

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    I wouldn't say off base, but fish don't simply look around at their tanks and regulate their sizes accordingly. By and large, fish size is governed by its genetic background. It's true that many fish won't acheive their full size because we don't give them the perfect environment in our tanks, but most will, and I think should be given the opportunity.
    As far as regional variation, you may be able to give counterexamples, but differences in size between locations tends to involve selection acting on size variants and causing smaller or larger forms to be more common in a given region. Further, environmental factors such as overharvesting can also skew size ratios in an area.
    That being said, you can certainly stress a fish into being stunted, but there may be side effects such as susceptibility to disease.
    To give a concrete fishkkeping example of how fish aren't limited by tank size, a customer brought a 30" arowana into the LFS I worked in. Amazingly, it had grown up in a 29, and had just enough room to turn around. It was very happy to be moved to the 200 gallon tank.
    That was a lot of words, but the upshot for me is that I try to select species that will be happy at their adult sizes in my tanks.
     
  3. Slappy*McFish

    Slappy*McFish Backhanded fish to the face!
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    30" arowana in a 29g? geez..thats seems impossible...not to mention very irresponsible of the owner...absolutely rediculous.

    The point isn't whether or not it is possible to keep a fish in a tank that is too small for it's potential maximum size....ofcourse it's possible...the point is not "can you", but "should you" keep such a fish in that sort of environment...IMO, no you shouldn't.
     
  4. Cearbhaill

    Cearbhaill Reads the Gribble Report

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    Those "closet children" they find locked up by psycho parents don't grow very well either.

    You're talking about the difference between thrive and survive.
    It's the difference between a one room jail cell and an estate... you could survive quite nicely in a jail cell all your life eating bread and water, but what sort of life would it have been? You would never have developed physically, you would be socially deprived, miserably depressed- basically just an alive human.

    Just being able to keep a fish/animal alive and eating is not what keeping captive animals is all about. At least some thought should be given to providing an environment where they can enjoy their life. This means providing habitat where they feel secure, food suited to their digestion, and room to move and feel comfortable.
    Their environment needs to be judged by fishy standards- not human standards. Some species need room to graze, some are solitary, some need a wider variety of foods, some even need predators to trigger certain behaviors. There is a whole, whole lot that we don't know about fishy mentality and what they need to thrive- live the optimum live possible.

    I believe it is an awesome responsibility to bring a captive animal (and that goes triple for wild caught animals) into our home. We control every single parameter in their world.
    We chose to take them on and care for them- the very least we can do is the best job possible.
    That doesn't mean everything can always be perfect- it won't.
    But skimping on providing something as basic as room to live is not the way to go. If you're willing to compromise on that- what's next? Substandard food?
    You'd end up with stunted, colorless, miserable fish.
    Is that why you got into the hobby?
     
  5. glittergirl

    glittergirl AC Members

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    Can I just ask - How do you know how much room the fish need? There is a lot of conflicting advice out there.
    My tank holds about 13 gallons and the information I got from lots of different sources, all said that my tank would comfortably hold 12 fish of about 5cm. I actually have 11 fish, all about 5cm, or they are expected to grow to about this size. I thought I was doing quite well with the amount of room allowed for the fish, but when I came on this forum, lots of people said my tank was overstocked. What is the best way to tell how many fish will live comfortably in any particular tank?
    I have quite a lot of plants in the tank as well and the fish swim through them and around them. All my fish are active and curious, their colours are very rich and defined, and they all eat well. I am only a newbie, but I think they are happy and thriving. :)
     
  6. mogurnda

    mogurnda vaguely present

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    I am hesitant to give a measure of inches of fish/gal or per surface area, because that gets so contentious. I tend to go for about 1 inch/gallon. Regardless of the way you measure it, you can get away with more smaller fish, because they have higher length/volume ratio than bigger fish, which means there's less metabolically active tissue per unit length. An 8" oscar needs more O2 and makes more ammonia than eight 1" tetras.
    The factors I consider limiting are
    1. Water quality. This is the most commonly cited reason. More fishmeat in the tank makes more waste. Most tanks nitrify well, getting rid of the most toxic NH3 and NO2. However, nitrate will stress some fish, and messes up your tank's buffering system, making it more acidic. Oxygen is less of a problem in a well-filtered tank with lots of turnover, but see "safety factor," below.
    2. Behavior/aesthetics. You want fish in numbers and combinations that will make *them* happy. In many cases this means fewer fish than the tank will hold. Very dependent on the species.
    3. Safety factor. If you are pushing the envelope, then what will happen when a snail gets in the impeller of your filter, power goes out, or whatnot? I had a 100 gal, filled with Haplochromis that I had raised from babies, which was truly spectacular until I was away and the filter failed. Heartbreak. You can't expect things to live indefinitely without filtration and heat, but keeping stocking low is good insurance.
    By the way, what kind of fish are they? It sounds like you have heard plenty of opinions about your stocking already, but I am just curious about what you have. If they are perky and colorful, that's great.

    ed.
    After thinking about it, boy, that sounds like an awful lot of fish. I'd keep a close eye on them.
     
    #6 mogurnda, Jun 5, 2003
    Last edited: Jun 5, 2003
  7. Mr.Jingles

    Mr.Jingles It's Aqua Live!

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    fact of the matter: fish need room, give it to them.

    inches per gallon is rediculous. think more along the lines of: if I found this fish in the wild, how much territory would it be occupying? Then adjust your tank size to its preffered territory and your budget.
     
  8. mogurnda

    mogurnda vaguely present

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    I keep editing this post, because it's hard to come up with a response that summarizes what I want to say, and is also useful to a newbie.
    I regret having given a numerical value, and wish I hadn't. But where does one start? If you are an experienced fishkeeper, your measure will work to some extent. But if you have not kept fish before, how will you imagine what a fish will need in the wild? In fact, most experienced aquarists do not have access to real data regarding home ranges of different species, and the overwhelming majority have fish in much smaller volumes than they would occupy in the wild.
    In the end, if someone were to ask me how to stock a tank, the answer would very much depend on the species and how much room it needs to color up, act "naturally" and, if possible, mate. This is based on years of experience. I would always push for fewer, rather than more, fish in a tank.
     
    #8 mogurnda, Jun 8, 2003
    Last edited: Jun 8, 2003
  9. Mr.Jingles

    Mr.Jingles It's Aqua Live!

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    yeah...youre right. It does take prior knowledge to understand what a wild territoy would be like.

    Lets put it this way:

    If you want your fish to be happy, put it in a tank that provides alot of room for swimming, enough surface area for gas exchange, and enough room for it to avoid aggression from other fish or enough room for it to not kill the fish with its aggression.

    in terms of multiple fish:

    if you want all your fish to be happy, make sure the fish dont conflict, their total waste doesn't increase the ammonia or nitrites, and (depending on your taste) they aren't always swimming in mixed groups.

    for intance, I consider my 50 gallon crowded with
    9 cherry barbs
    7 1 inch acaras
    4 half dollar angels
    3 adult cories
    3 adult otos
    5 adult shrimp
    many 1/4 inch baby platies.

    my tank is planted, so space is taken up by plants, but the fish are always swimming together, which makes it overcrowded to me, even tho all the other reqs. are met. the mixed group thing is a personal preference tho.

    as the fish get bigger, you should weigh the mixing into your equation more heavily.
     
  10. cindywindy

    cindywindy AC Members

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    This reminds me of the "one gallon per inch" rule that we try so hard to negate, and never seems to go away.

    If this is so, can one expect to put a 10-inch Oscar in a 10g tank ? Never !

    The answer to this and so many questions about providing the most optimal environment for your fish lies in research. Read all you can to find out the size range of the fish, and then if you still have doubts about the size of tank necessary to house such a fish, come here and ask. That is what we are here for !
     

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