BushFishRox;1102605; said:

so for a 12" fish you would have 12' or 144" of space for that one fish? so that would be like 6x2 (180galish) for 1 12" tropical fish?

um, I'm not sure if it's your math that got messed up, but my interpretation is that you need 12 sq inches of surface area for one inch of fish. So that 12" fish needs only 1/12 of that 6x2 tank. Or said another way that tank could hold 12 x 12" oscars, or 6x24" gars.

It is also interesting to combine the two methods (guppy's fish volume with the surface are method). I mean that would be more reasonable than just length. Although the math is a little taxing to be doing in your head when down at the lfs.

Personaly I think the surface area calculation is good for newbies to ensure that they don't crowd the tank and suffocate the fish, and the volume calculation is more useful for those of us who are looking to keep more delicate fish which require us to keep a tight control over the build up of Nitrates etc. which has more to do with volume than surface area.

BTW, how many of us truly know the volume of our tanks? I mean I own a 65 gallon, I could easily have displaced 5 - 10 gallons with decor, added 25 - 35 gallons with the sump, so altogether somewhere between 85 and 110 gallons ... it's a pretty inexact science for most of us.

Anyone else hear of interesting rules for deciding how many fish a tank can comfortably handle?