Betta_dude

Everyone knows the 1-inch of fish rule of thumb,right. Well I read about another, your tank's lenght x its width x 3-inches. what do guys think of it?

susitna-flower

I don't quite follow the idea....
If I had a tank that is 72" X 24" what would that be?

72X24X3=5184 would that be the number of inches? OR were you meaning it would be....72x24 DIVIDED by 3 which would be 96" of fish....

With my stocking rate for my 125 gallon tank I can have approx 125 inches of adult size fish, except I have 2 that have to be counted as "cubic inches" both the bala sharks are now about 12 inches, but thick. I feel it is always better to stock lightly, it makes for lots easier tank maintenance.

Betta_dude

I might have goofed, I'll have to double check

Lucy

Too much math for me, the 1" per gallon is easier.

Betta_dude

The book says"3-inches of fish per square foot of filter bed." example: 12-inch width, 30-inches length-

12inchesx30inches=2.5 multiply by 3

2.5 square feetx 3inches=7.5 inches but thats just what the booki says.

Lucy

Seriously, way too much math for me lol

Butterfly

12 inches x 30 inches / by ? to get 2.5 sq ft. ?

You still need a height to figure out how many fish you can keep in any specific tank because you need to know how many gallons of water is covering that foot print.
12 inches x 30 inches x 18 inches = 29G
12 inches x 30 inches x 12 inches = 19 G
The smaller tank would significantly alter what/how many fish you could keep.
There are many theories about how to figure how many fish to keep in a tank and some are more helpful than others.
When stocking, the fishes adult size and body mass and waste production has to be taken into consideration as well as length.
Example : It would be easy to keep 10 Neons in a 10G tank. Their small, will remain small, don't produce much waste.
It would be impossible and cruel to keep even one Clown Loach, Oscar, Pacu or most plecos in a 10G because of their potential adult size, their body mass from the beginning is dense, and their waste production because of that body mass is extremely high.
Just some thoughts.
carol

sirdarksol

What Butterfly just said is why I hate calling the aforementioned guideline a "rule", even "rule of thumb." No mathematical equation that a normal person could easily figure out without a graphing calculator can precisely determine what number of what species can go in what tank. It requires human thought and guesswork, with the aid of some guidelines, to make these decisions.
In addition to body mass, you have to consider waste production of individual fish (which is influence by the normal diet of that fish), nature of the fish (a hunter that prefers being concealed in one spot all day can stand a smaller tank than an energetic fish that roams back and forth, looking for tasty bits to eat), and even eating habits (a messy eater will leave little bits around a tank. These bits will decompose and add to the tank's bioload, unless you include some sort of scavenger, whose own bioload you have to figure in)