I always guesstimate it... but honestly, if you cut the top off... then the bottom off, it normally fits perfectly, I had to trim it down a bit for my five gallon, but that was it
Turning it off for a short term will be fine, its when the actual filter inside is left alone unmoving or when it drys out that the bacteria starts to die
Hercules, Finn, Flagg, Sammy, Jackpot, Anchovy, Gotham, James, Honey, Echo, Ender, Merle, Orpheus, Dancer, Peanut, Dragon, Omen, Eurydice, Smudge
My FIRST spawn!!!!
Unknown number of fry... HM marble + HM marble
Ned, Lucky, and Dusty (AKA Nemo)
Chai, Punk, Pandora