Are these tubings you can put on the outflow of the powerhead common? Do they sell them at any petstore? Also, can you control the flow rate of the powerhead like a dial or lever or some controls, whatever? I'm curious about powerheads, like you said, I have freshwater, so I don't have them, thus, the curiosity. Oh yea, can you also post a pic of this tubing on the powerhead, and also wherever you put it to lead to if it's not too much trouble.