One Inch Per Gallon Rule?

Discussion in 'Freshwater Fish Disease' started by Didgeridoo, Jan 21, 2009.

  1. DidgeridooNew MemberMember

    Hey there! I've heard some conflicting information about the inch per gallon rule. Specifically, that it doesn't refer to length, but actually sq. inches of fish. This is a sticky over at the Monster fish Keepers forum, and I wanted to hear some opinions about it. This was written by the user "Guppy."

    What do you all think about that? It seems to make sense, but then again I am very, very new to fishkeeping. I'm a bit confused...
  2. sirdarksolFishlore LegendMember

    We've had the discussion before, and the cubic inch thing works better, but it still isn't perfect.
    Around here, we call it (or try to) the "one inch per gallon guideline," and we generally only apply it to small, commonly-kept community fish. Even going with the cubic inch, there are fish that don't fit it either due to biology or personality (think bettas)

    To go with Guppy's example, a 2' long arrowana would be absolutely miserable in a 100g tank. It wouldn't even be able to turn around without bumping into the side of the tank.

    To go with another example of Guppy's, I certainly wouldn't want to cram 50 fish of any kind, even the glowlight tetras, into a 10g tank.

    As you can see, there is a bit of a failure in Guppy's logic. (sorry, I couldn't resist mimicking that)

    The reason we call this concept a guideline is that there is more information involved in the stocking process than the simple idea of size.
    Last edited: Jan 21, 2009
  3. docjr03Valued MemberMember

    It does make sense, but I am in the same boat as you, being a newbie and all! It would be nice if there were a more scientific guideline out there that gave us info on the volume of ammonia each type of fish produced...
  4. sirdarksolFishlore LegendMember

    There is, but the problem is that it takes into account several factors that make it difficult to put down as a simple formula. It involves the fishes' diet, their size, the biology of the species (different animals possess differences in digestive efficiency), etc... That's why, in the end, the best way is to research the individual species when you're making a decision on what to add.
  5. prairielillyWell Known MemberMember

    I have found that there are a million (ok...a lot) different methods for calculating EXACTLY how many fish you can put in such and such a tank - figuring out what to do can be incredibly confusing! The danger with these methods, as sirdarksol said, is that they don't take into account many things more important than the actual size of the fish - like temperament, behaviour, bioload etc. They also don't factor in things like how much decor you have (more decor, less actual water) or maintenance.

    All that said, I always feel it's dangerous in any situation to over-science-ize something, as in putting too much importance on some calculation. The best method (I've found) is to START with the 1"/gallon guideline and come up with a list of what you think will work, then ask more experienced fishkeepers what they think of it. As you become more experienced, you'll be able to determine for yourself what will work and what won't.
  6. docjr03Valued MemberMember

    Well said...:;rocker
  7. DidgeridooNew MemberMember

    Thanks for weighing in, everyone! I thought the tetra thing seemed a bit over the top. Can you imagine 100 tetras in a 20 gallon tank? :;bmu
  8. docjr03Valued MemberMember

    Imagine???? I have 102!:;nin2
  9. pinkfloydpufferFishlore VIPMember

    When stocking... well, I usually have species tanks, so that makes it easy. But, if I were going for a community, I start with only a few fish. Then wait a while, add a few more. I keep an eye on the water quality. As long as the fish have the proper space, just watching the nitrates should tell you when you're fully stocked. With all of my tanks I can get away with water changes every other week (although I usually do it weekly anyways). For example, my 10g tank. If you look at it in my aquarium info in terms of fish it's quite overstocked. But, they all have sufficient room, and I never see nitrates over 10ppm, even if I let it go 2 weeks between water changes.
    So, I say, forget the rule, figure it out through experience! ;D
  10. Fla_LarryValued MemberMember

  11. DozeyWell Known MemberMember

    Although still new myself this is exactly the “science” I am planning to use. I have a 35 gallon tank and will be stocking it with very small fish so I know room to swim and turn around will not be a problem.

    Currently I only have 6 neons, 1 clown pleco and an apple snail. My nitrates never get over 5ppm so I know I’m far from my stocking limit.

    I will continue to stock a few fish at a time until I find my nitrates reaching 10 to 15ppm in a week. I will be able to control this with water changes.

    Of course I am also considering the habits of the fish I will be adding (where they swim in the tank). I wouldn’t use this method and stock my tank with fish that are only middle swimmers. Then over crowding could become a problem.

    So my pleco keeps to the bottom of the tank. The neons are right there in the middle of the tank. And my next addition will be 2 honey gouramis that like to hang out near the top of the tank. And as far as the apple snail well he’s just every where.
  12. dancerhasWell Known MemberMember

    Great points everybody!

    Here's how that formula would apply to our 4'' Chinese Algae Eaters:

    2x(4x1/2x1/2) = 2 Gallons

    Two 4-inch CAE's in a 2 gallon tank??? HA! In the case of long skinny fish, it's safer to go with one inch of length per gallon of water. This would bring us to 8. Much better, but not even close to what two CAE's need due to their bio-load and swimming habits.
  13. gremlinWell Known MemberMember

    No kidding! CAE's are HUGE fish in a small body! I don't think I would keep one in anything less than a 40 gallon. And if there were two, then I would go with a 75 gallon or larger.
  14. Iron waffleWell Known MemberMember

    I wish people would stop looking into "rules" for stocking fish, none are accurate enough to be worth following them. Really, common sense is the best guideline...
  15. LucyModeratorModerator Member

    Where's Amanda? She dislikes the 1" rule too.

    Personally, I like to use it as a guideline, not a rule and only for small non bulky fish. To me, it helps to give new fish keepers something to go on and avoid overstocking a smaller tank.
    After someone gets a good understanding of the nitrogen cycle, swim space and compatibility then they'll know what their tank can and cannot handle.
  16. docjr03Valued MemberMember

    Couldn't think of a better way to do it. PFP seems to have it down!;:barf:;rules

    (I will be using this method when I finally get to start stocking my tank thanks to her advice previously!)
  17. sirdarksolFishlore LegendMember

    Well said. This is pretty much where I'm coming from when discussing such guidelines.
  18. Nick GWell Known MemberMember

    The best stocking rule i've found is to combine the 1 inch guideline with common sense. I have a 75gal tank with 24 inchs of fish, the 24 inchs come from 2 Oscars though and I wouldn't put them in a 24gal tank! I also have a 20gal with about 26 inchs of fish which is 'overstocked' according to the rule, but they're all small fish with small bio-loads who live quite happily together.
  19. Drew 43920Well Known MemberMember

    Which tank ?

    Which tank do you have them in ?
  20. DaneNew MemberMember

    I'm really glad that this topic has been opened. I find people are very quick to accuse others of overstocking (although they are often right!) without personal knowledge of the setup etc. Too many "1-inch- 's" out there! ;-) Stocking is a very dynamic thing, dependent on many variables, agree that is definitely a good base or guideline, which must be used synergistically with common sense, observation and experience (not that I have much of that last one myself!). :)