Originally Posted by Hungry Seacow
Now with that said, I don't think that either method is accurate.
Agreed. Much depends on species of fish being kept , amount of filtration, and amount of maintenance you are willing to do. That being said though I do prefer longer tanks over tall tanks and I feel they almost always allow for more stocking options.
As far as the grand website for figuring out stocking levels.....if there was one it wouldn't be accurate anyway for the same reasons the one inch rule isn't accurate. It would still depend on how much time/maintenance one is willing to dedicate to a tank.
However you can buy testing kits and moniter your tank closely and this should be the best indicator of how your tank is doing. If you can keep your ammonia/nitrites at 0 and your nitrates under 40 then your tank is okay. If your nitrates are easily kept under 10 then by all means add another fish. If your nitrates are always through the roof then your probably overstocked.
Also you can tell if your fish are colorful,active, and spawning then your tank is okay. If they are crowded, faded colors, and inactive then they are probably stressed and things need to change.
You can also view disease as an indicator of tank health. IMO
many diseases you hear about over and over again are due to poor water conditions and someone who is not doing the amount of water changes they need to do for their tanks stock.