Measuring fish length

[qguy]

Aside from catching the fish, any other way to measure a fish that is between 15 and 20 inches?

 

[jr71]

Aside from catching the fish, any other way to measure a fish that is between 15 and 20 inches?

Depending on its movement/location in the tank, one method I've used is to lay a tape measure in front of the tank and take a video. You can then freeze frame when you get the best view to estimate from the tape measure. Of course, this will only work reasonably well if the fish is near the front of the tank and lined up straight across. I had a flowerhorn that would comply perfectly, so I could chart growth pretty accurately without netting him.

 

[qguy]

Took several shots, eventually he lined up quite close to the glass