Just wondering if there is(are) any tried and true safe way(s) to measure live fish length without stressing the hell out of them and minimizing possible harm.

I wish I could tell my Oscars (and other fish) length more accurately. Right now I sit for a while with a measurement tape and wait until they somehow approach the front aquarium wall and stay still for second or two... kind of sloppy way of doing it. I wouldn't like to harm my fish or stress them out in order to satisfy my curiosity...

Pepe
Santo Domingo

you might try taping a cloth measuring tape to the front of your aquarium and im sure after a while you will eventually get to see the fish in along the tape and you can measure that way. or take a pic when the fish is along the tape

I had tried so many times until now... I find it difficult to measure them accuately. I had tried several times the way necromancer4 suggested and failed.... due to my frustration, i get them out of the water, measure them actual and weight them: 15 & 14 inches;... 1600 grams & 1500 grams respectively.

i do what necromancer said, seems to work ok for me:)

plastic or wood ruler. drop it into your tank number side up and wait. it will not take long before all your fish come to look and then you just watch them swim over it.

I stick several lengths of tape against the glass, 8, 10, 12 inches. If you stick it where the Oscars feed, it will give you a good indication of how long there are. Obviously if you want to be absolutely sure, the only way is to remove the fish from the tank and use a tape measure. Personally, I don't really like doing that because it does stress fish out a lot, no fish likes being taken out of the water , so unless you've got a really good reason for wanting to know exactly how long you Oscar is, I would advise people not to do it. It's not difficult to estimate the length of an Oscar doing otherwise without the need for removing it from the tank.

necromancer is spot on. Tape one of those tapes that tailors use to measure people with across the tank. your fish will soon get used to it and ignore it. Wait until your fish swim along it and read the measurement for the front and back of your fish and the length is the difference. Or take a photo and work out the length

This is how I did it...

Wow paul, your oscars are beasts.

whats your secret?!

Feed them with frozen beef heart or pork spleen alternately.

Pooky_84, your oscar looks like my oscars. The only difference is mine had thick large scale (10mm in size) & little bit whiter.