Inch per Gal Theory???

[GER1023]

In a German Disease book by Untergasser is a very interesting by thumb rule for stocking tanks:

fish size = water per inch fish
under 1” = 1/4gal per cm
1-2” = .4gal
2.3-3.5” = .5gal
4-5” = .8gal
5.5 and over = 1gal
(and i guess over 12” this just goes up...)
by this rule a 16” Red Tail would need 42gal by himself (at least)

This was on another forum I don’t see how this would work out. It was on the the PlanetCatfish Forum I went on to get info and this is what I got.

[JackDonkey]

I think that anyone that needs to go by a inch to gallon ratio for fish size already has an overstocked tank based on how the fish look and act, and they are using the ratio to justify that they are under the inch/gallon limit so their fish should be fine, even though by looking at the fish they probably are not.

Or they wish to get a bunch of fish at once and want to know the max. Which is also a bad idea, just buy like one or two fishies a week and then when they look crowded they probably are.

now GER1023 I'm not pointing a finger at you because I realize you probably posted the above information because you thought it didn't sound right.

[GER1023]

Yeah I was just surprised that this is the info I got. Me myself for cichlids for the most part say for a min is 5gal per in so a 12" oscar would need a 60gal a 18" managua would need a 90gal granted you do tank size with adult size and not the size you purchase them at. I was trying to figure out a similiar rule for Pleco's since everywhere I read it say a 18" Gibbiceps only needs a 60gal which Seems of a bit. Dont know.


Ok just with this info on the gibbiceps it is basicly 3.3 gal per inch for plecos then. Still seems to little though.

[CyberDrgn]

You can't use any type of inch per gallon rule for fish that aren't small thin bodied type. fish that reach 12" plus you just need to ask others with experiance and use your own experiance to find what best works for you.

[GER1023]

Yeah true but the 5gal per inch usaully work out except for fish like umbee's and dovii's.

[RTR]

If you have access to the out-of-print "Idiots Guide to Freshwater Aquariums" by Mike Wickham, it gives a better guide, based on mass rather than inches. But even that has weaknesses.

I agree that the antique inch per gallon rule is useful only for small, slender-bodied fish of adult size less than 2 1/2 inches standard, and if full adult size is used for the calculation. And "full adult size" is from a real reference such as Fishbase.

The rule of thumb is worthless for carnivores or territorial fish under any circumstances.