I have a penguin 350 filter with sand substrate and I took out the middle tube and put the strainer more toward the top of the tank. Is there any advantage to having it cloer to the bottom or to the top? Thanks
if they're close to the bottom, they'll catch more poop chunks before they settle down into the gravel...
but you have sand and if it starts sucking in sand it could stop up your impeller. i'd keep it up high in your case.
edit: i had that same filter on a 29g w/ play sand and a pair of convicts. even with the strainer in the top position, it still sucked up a bunch of sand. that could be due to the fineness of the sand and/or the cons stirring it up. anyways, it was enough hassle for me to get rid of the sand.