I don't want to appear picky here because that is a magnificent specimen of a clown loach. But when measuring fish, as a keen angler, we measure from nose to fork for "true" length, so that beauty is 12"....right? And not 14". To be fair i'd call it 14" and be done with it because whatever it is, 12 or 14, most of us will never have such a thing of beauty in our tanks.
When measuring fish their are several methods that one can use, standard length (SL), total length (TL), and even fork length (FL), are routinely used by State & Provincial fisheries as well as in commercial aquaculture circles.
Instructions on how to properly measure your catch …
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In many parts of North America, including the USA, TL is used as a determination on the length of a fish, for anglers. The correct manner in which to get that measurement is to lay the fish flat, and push the tail fin lobes together.
Table of Contents Licenses Fees General Regulations Bait Definitions and Regulations Manner of Taking Hook and Line Fishing
gf.nd.gov
How to Measure the Length of a Fish
To determine the “total length” of a fish, lay it flat on its side with its mouth closed and measure from the nose to the tip of the tail when the tail lobes are pressed together.
Factors affecting standard weight
Example of fish length measurements. For standard weight equations, the total length is used. This fish is a tarpon.
Length measurements reported for fish may be of the fish’s
total length,
fork length, or
maximum standard length.
For standard weight equations, the total length is used.
In some species, male and female fish have different standard weight curves. For example, Anderson and Neumann report different standard weight equations for male and female
paddlefish.
[5] Some researchers have also reported separate standard weight equations when a species has lentic (living in still water) and lotic (living in flowing water) populations. For example, separate standard weight equations have been published for lentic and lotic
rainbow trout.
[6]
Personally, in the hobby, I have always used the TL method when measuring a fish.