waterdrop
Enthusiastic "Re-Beginner"
We've had many long discussions on TFF where many of us have pretty much agreed to call this animal the "loose guideline" (*not* the one inch rule) because there are so many extra things to think about with it.. its weird, its just not a rule and yet for a beginner to ignore or not take the overall issue seriously is a bad problem in the making.
In my opinion, based on old experience and also a lot of cases that come by here month after month, its extremely important from the beginners standpoint to try and have a good first year within the tropical fish hobby and thus to get the feel of what its really like when it goes well. Eventually, most hobbyists will experience the feel of overstocking and other types of stocking problems, but when a beginner experiences this badly in the first year, it often turns them off to the hobby forever.
Overstocking has a "thrill" to it that seems very enticing to the beginner. After all, many of us have seen vast numbers of fish when snorkling or beautiful crowded arrays of fish in public aquaria or exciting shoals packing an experienced aquarists big show tank. Its very difficult for a beginner to have the background info to understand that mother natures environments are entirely different, the public aquaria have spent vastly greater amounts of money on their environments and finally that the very experienced aquarist who is overstocking may have truly built up a lot more "experience" for how to go about it successfully.
Overstocking however, especially for the beginner, is not really all that its cracked up to be. There's often a need for quite large and more expensive filtration equipment that the beginner has not learned about yet. There's the very real risk that comes from losing electrical power. An overstocked tank is much, much more difficult to deal with in these situations, by the way. Finally, the "look" of the overstocked tank is *only one* of the many interesting types of looks that can give great pleasure in an aquarium and sometimes it can really look rather crowded and unnatural compared to a correctly or understocked tank.
As a practical matter, the very loose/rough guideline of one inch of fully mature adult fish body (fins/tails don't count) per US gallon is actually a very cheap, very simple, very quickly understood and used guideline in my opinion. Its only ever been meant as a rough mental starting point in the long journey to a final stocking list. The beginner needs to fully understand that its got to be the maximum size a fish can get to and not its young size when seen or bought in the LFS. One must take the time to visit some sources of good fish adult size info and take notes for each fish. Ideally one then also must consider whether the fish are smaller or larger than average and use that to slightly exaggerate the final estimated contribution up or down and even more ideally one would take into account the special instances that people know about such as that certain large suckerfish will put out way more waste than even their large size would lead one to expect! There are a few good special considerations like that but otherwise there are diminishing returns to laboring over it too long.
Of course, the beginner also needs to be aware that this thing we call "how many fish can I put in" is only one phase or topic among several important ones on the path to a final stocking list. The other major phases are figuring out the minimum shoaling sizes of many of the fish types and then matching what size shoals you might attempt against the other fish and shoals you hope to have. And another phase of going through each species against every other species in the tank and figuring out if they can live together or what type of behaviour to expect if you attempt to have them together in whatever numbers you are homing in on. Dragging all this sort of info and advice out of even the very nice members who post here on TFF can be a difficult and time-consuming thing and to do it well requires that the beginner do plenty of homework to help things along. No beginner is going to get it all right but you have to start somewhere and just plan to get better on each successive tank you plan and set up.
~~waterdrop~~
In my opinion, based on old experience and also a lot of cases that come by here month after month, its extremely important from the beginners standpoint to try and have a good first year within the tropical fish hobby and thus to get the feel of what its really like when it goes well. Eventually, most hobbyists will experience the feel of overstocking and other types of stocking problems, but when a beginner experiences this badly in the first year, it often turns them off to the hobby forever.
Overstocking has a "thrill" to it that seems very enticing to the beginner. After all, many of us have seen vast numbers of fish when snorkling or beautiful crowded arrays of fish in public aquaria or exciting shoals packing an experienced aquarists big show tank. Its very difficult for a beginner to have the background info to understand that mother natures environments are entirely different, the public aquaria have spent vastly greater amounts of money on their environments and finally that the very experienced aquarist who is overstocking may have truly built up a lot more "experience" for how to go about it successfully.
Overstocking however, especially for the beginner, is not really all that its cracked up to be. There's often a need for quite large and more expensive filtration equipment that the beginner has not learned about yet. There's the very real risk that comes from losing electrical power. An overstocked tank is much, much more difficult to deal with in these situations, by the way. Finally, the "look" of the overstocked tank is *only one* of the many interesting types of looks that can give great pleasure in an aquarium and sometimes it can really look rather crowded and unnatural compared to a correctly or understocked tank.
As a practical matter, the very loose/rough guideline of one inch of fully mature adult fish body (fins/tails don't count) per US gallon is actually a very cheap, very simple, very quickly understood and used guideline in my opinion. Its only ever been meant as a rough mental starting point in the long journey to a final stocking list. The beginner needs to fully understand that its got to be the maximum size a fish can get to and not its young size when seen or bought in the LFS. One must take the time to visit some sources of good fish adult size info and take notes for each fish. Ideally one then also must consider whether the fish are smaller or larger than average and use that to slightly exaggerate the final estimated contribution up or down and even more ideally one would take into account the special instances that people know about such as that certain large suckerfish will put out way more waste than even their large size would lead one to expect! There are a few good special considerations like that but otherwise there are diminishing returns to laboring over it too long.
Of course, the beginner also needs to be aware that this thing we call "how many fish can I put in" is only one phase or topic among several important ones on the path to a final stocking list. The other major phases are figuring out the minimum shoaling sizes of many of the fish types and then matching what size shoals you might attempt against the other fish and shoals you hope to have. And another phase of going through each species against every other species in the tank and figuring out if they can live together or what type of behaviour to expect if you attempt to have them together in whatever numbers you are homing in on. Dragging all this sort of info and advice out of even the very nice members who post here on TFF can be a difficult and time-consuming thing and to do it well requires that the beginner do plenty of homework to help things along. No beginner is going to get it all right but you have to start somewhere and just plan to get better on each successive tank you plan and set up.
~~waterdrop~~
Yet, something that fits, is computer says I'm 356 gallons worth of fish over-stocked. OK, one filter of the two copes fine alone biologically, so I'll agree that the filtration calculation is OK, the Nitrate levels run away if I cut back on water changes, so that may want attention, I'm not sure what a unit of waste equates to, I imagine it is something like Bio-load? Anyhow, I'll ignore that until you explain, and the "overstocked" reading is probably right. I was expecting to be told that Angels and Discus aren't recommended, but I can't see where it recommends not putting stuff together 
Might be worth adding explanations for things like your waste units e.t.c to make it more clear to a new comer. If it confuses someone like me that's been playing with fish for 14 years, I imagine it will petrify a new comer... Pointing out where it shows errors could make the errors being thrown easier to understand and correct also 
