hey,
first I must say you have a great attitude to deal with constructive criticism, and need to be commended for that. If you were in NZ I would even buy you a beer to show how genuine that is, however i do not drink beer as it tastes ghastly, so you would have to drink it all alone, and that's depressing...but that is another story. :lol:
The calculator needs to account for the size of the fish, the food they are being fed (what goes in comes out), the filtration - but more importantly the media - take me for example.
2x fluval 405s and 1 eheim 2028 with more than 3L of eheim substrat pro media means 450sqm of surface area per Litre of media. that's place for the bacteria to live - and that's a lot of good bacteria in the tank in a tank that probably holds less that 200L of water after accounting for all the volume that the plants, substrate and items in the tank account for.
The same amount of filtration would be near useless without any media.
perhaps the algorithm of the calculator could include a data input variable where users could choose to enter the size of the fish in question.
eg. a 4cm royal panaque will not produce as much waste as a 12" + royal, and is ok in a smaller tank, but needs a larger tank as it grows.
the calculator also does not account for plants in the tank. more plants of the right sort = lower nitrates, and a more stable environment.
It would be near impossible to account for all the variables and make everyone happy, but you are on the right track.