I did partially overcome this problem by using my spreadsheet. Take the surface area, then divide it by 6. That is the worst-case fish-inches that the tank can handle. (This is twice the recomended load by fishdude).

Then I have a separate table of all fishes I know. I derive a "species factor" which is different for each species. As an example, platies will get 2 while we can give 1 (or even less) for cardinals. Plecos get at least 3 if not 4. Take the actual length of the fish when they are fully grown, then multiply it by this factor. Total up these numbers for all the fishes you have in your tank to see if you are reaching your limit.

For my stocking plan, using this method, I ended up with the capacity of roughly 60% when they are fully mature. I have checked with more experienced people in the forums to see if my stock will be ok and so far, it is positive. (Obviously, I didn't talk about this method I'm using).

I've also noted all threads that talks about a tank being overstocked. I used the same method to see what the ratio is, and almost always, it is above 80% - in some cases, over 100%!.

Nice practical example:

- 10 inch Oscar in 10g tank:

- surface area / 6 = 20 * 10 / 6 = 33.3 worth of "fish inches".

- Oscar gets species factor of at least 4, since it is nortoriously dirty. So at 10 inch, it's 40.

- At 120% capacity, this tank obviously will not work.

- 10 neon tetras in 10g tank:

- fish inches = 33.3

- Neons get species factor at 0.8 since it's real thin and clean. Assuming it grows to 1.5 inches, you get 1.5 * 10 * 0.8 = 12.

- At 36% capacity, this tank should be easy to take care of (at least from bioload perspective).

- glittergirl's tank:

- fish inches = 40 (estimate based on his volumn)

- 11 fishes at 2 inches each. (Are these fat or thin fishes?)

- Assuming average, the species factor should be at 1.5. This gives in total, 1.5 * 11 * 2 = 33 fish inches worth in the tank.

- At 83% capacity, this is somewhat crowded. It would require more careful maintenance.

This obviously doesn't take into account how often the water get changed, plant factors nor territorial behaviours, but at least it seems to take care of the dirtiness of fishes quite nicely regardless of their actual size...

I can post the table I use, if anyone's interested...

There... I made yet another attempt to quantify thing that aren't quantifiable... (hey it goes with your job, I can't help it..) Any comments?