I have sand on my tank with a pengiun 350 and I was thinking if I had it on the low setting it would suck up the sand especially when the fancys dig it up looking for food and might cause damage to the filter. So would the middle setting work? Or would it affect the water circulation as there is more feces at the bottom then in the middle/higher towards the top of tank. Also how would I set up my bendible/flexible bubble wall tube. Ive heard to try to avoid air bubbles from getting into the filter so would I create a "barrior" bringing the tube a few inches from the intake tube? but then wouldnt the water inside the "barrior" from the bubble wall actually create a barrior and the feces and other things stat within the bubble wall and unable to get the the filter intake as the bubbles are going up and not letting anything past it/go behing the bubbles where the filter intake tube is. Its placed in the middle of the tank btw. With a low being close to the bottom and high setting being the middle of tank going up and down. Thanks.