Update: I was looking around on here and came across a few of Boomers pics of his cooler setup. I understand the draining part. Get an extension hose to hook up and drain. So I'm assuming that he has a water hose that he hooks up to the extension and fills it back up thru his drain hole?? What about the leftover that is left in the bottom of the tank after draining it, just recirculate it with the incoming water? It makes sense in theory.
Igloo it is. Was gonna do Coleman cooler but apparently they dont have the adapter for a water hose like Igloo does. This is a posting from Boomer that I wanted to share. I hope you don't mind me sharing BB:
I won't have as big of setup or as many pumps or stones but still the same setup I hope anyways
How many people have heat and light issues in the rubbermaids/tupperware?
if you are having problems check this out,,,,
i use the Igloo 5 day coolers. wal-mart sells the 120qt for about $50.00.
next go to lowes and get the 1 1/2 to 2 inch styrofoam insulation sheet, reflector or white 4x8 sheet about $10.00.
get a roll of the aluminum duct tape, not the regular duct tape. regular won't hold up to the moisture.
Step one,,
Remove the screws from the hinges where they screw into the cooler. Unscrew the lid strap from the inside of the cooler. remove lid completely and put it in storage.
step 2
set the sheet of insulation down on a flat surface. place the cooler UPSIDE DOWN on the styrofoam and draw the outline with a pencil giving the new lid a 4 inch overlap all the way around the cooler. use a razor blade or sharp knife to make the cut.
do this step for all the coolers you are going to use wether it's one or more.
step 3
tape the new lid completely. top bottom and sides
step 4
NetPots.
I'm using 5.5 inch netpots. i can put up to eight netpots in the lid. you will need an access hole to drop an ice bottle or measure temp and nutes if you don't have a tri-meter. cloning i recommend no more than 7 plants in the cooler. when transferring to my flower room i only put two plants per cooler, no more, then i scrog em.
step 5
place the netpots upside down evenly spaced and towards the middle. using a razor knife, trace the outline of the net pot and cut at an inward angle, not straight down. you want the netpots to be snug and flush. make sure your cuts are within the coolers cavity, don't get close to the edges, you need the overlap.
thats it,,,,,
light proof, temps stay constant mid 60's for days on end. easy fill and flush with standard garden hose fitting. can't tip em over and puncture proof.
do the math. you buy the coolers once. when yer done growing. you'll still have a functional cooler for yer faverite adult bev's,,,,,,, mines newcastle and makers mark,,,,,, having one of each as i type this tripe,,,,, plus ripping on the one hitter,,,
harvest tomorrow so it'll all be good,,,,
Light and heat or excessive cold in the res is a problem i see a lot so i hope this helps.
res temps should be no lower than 65 f and no higher than 70 f. bam,
save some 1 liter plastic bottles with a cap. fill 3/4 of the way with water and freeze. when you see yer temp near 70 f, drop an ice bottle in and it should take it back down to 65 f.
i run 12-16 air stones using the dual diaphragm, 4 outlet pumps. so 3-4 pumps per cooler. elite 6 inch stones.
+REP MAN I was just thinking how can I make my resv cooler for cloning I was thinking of getting a water aquarium cooler to much $$$ thanks bro I really needed that, Happy harvest man whatcha harvets? Hey how do you clone? If aero tell me your steps and how is your sucess rate with cloning? Hey your tap water do you let it sit out for 24hrs? Make sure you do it takes out all the BS I think chlorine or something, if your leaves turn brown with spots thats why, or ph, or a bunch of other shit! 
but make sure you let your tap water sit for 24hrs at least, Thanks for that info bro good job! kiss-ass
