I have decided to build in a safety into the pumping out of water... I'm using an 8 inch stainless pipe, with a screened end, to draw water from the tanks, for water changes, the weight will keep it positioned, in the tank, and with an elbow on the top, an 8 inch draw pipe, and the screened end, will at maximum, draw water down between 8-9 inches in the tanks.. this will be for regular water changes... I will also have an end I can exchange, that will vacuum gravel, & could be used to pump a tank fully empty if desired... 8-9 inches down, aught to be an acceptable water change percentage, at maximum...
next thought, will be the temperature of the holding tank, which would likely be 68-73 degrees through out the year... I expect most tanks would be OK, with those temperatures, at a 40-50% water change level, but I may need to put a warming mat under the tank, to keep the RO tank at closer to the average aquarium temp???
thoughts???