i am so confused! i went into petco today to get some sand substrate for my 75 gal. i never bought any, but here is the reason why: they had a choice between "live sand substrate" which is supossed to benefit the health of plant roots, and then they had coral substrate which is rougher and bigger so it won't get sucked up by a gravel pump (according to the pakage). i want the sand substrate because it is finer and looks nicer from my perspective, but i was just wondering if that whole "benefits plant roots" is true or not, and if i choose to get the substrate, it has water in the bag....do i dump the substrate AND water into the tank, or do i dump out the water and wash the substrate before adding it to my 75 gal?