Flow meter

[-Aquaman-]

So I'm getting ready to go from a 75 to a 125 and I am going to plum my frag tank to the same return pump. I was wondering since I dont have a apex or ghl to use their flow meters is there a such thing as a mechanical flow meter?

 

[virtual reality]

Just put a gallon jug and time how long it takes to fill it out of your returns.