Thank you so much! Just the thing I been looking for! How many pads would I need to filter a 75 gallon tank? Maybe I should ask, how many are in a gallon, and how many gallon would I need of them. What do you think about using 4" PVC pipe and filling it with those pads. Put the pvc pipe above the tank vertical and them use a powerhead to pump water up to the top of the pipe and let gravity bring it through the pads and back into the tank? I would put a reducer on the one end so I would not have a 4 inch pipe going into my tank. Think this would work instead of building a DIY overflow and then making a sump? Seems like a lot less work to me!...
Thanks