i always have my tubs on a table i have big drainholes which empty the whole tote in seconds but i dont use bought tubs i build mine from wood and geomembrane sheets with good plumbing stuff, big flexible hose for draining never ever leaks and the tub is very sturdy geomembrane sheets are black intended for huge outdoor ponds under sunlight guaranteed 3 years so i guess in my indoor lightproof tray i grow old before they ever break
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oh and for the pump size you can get small cheap ones no need for pump power in this system, one pump timer and gravity