Osmolator Universal 3155 i purchased at marine depot suppost to be delivered today but i think i can cancle it, anyways i bought this for water level in my sump to stay constant and so i dont have to keep dumping 5 galllon water jugs in sump and always making them outside from garden hose ro/di unit. THING is i have limited space live in small condo dont have room for a big ro/di storage container, maybe 5 gallon under sink or 10 galllon tall trash can behind tank and reposition my metal halide ballast on the side wich i dont really want to do. but still if i have this container in the back i still have to monitor it and fill it up, so back to squar one again, i know tunze makes a auto shutoff for ro/di but there hardly any detail about how it works, should i have gotton this one?also this is not my place i do not own, i rent so the system must be full proof, no flooding. from what i was reading and thinking i could just hook up a rainbird sprinkler valve and timer and have it go on for a certain time, it would be the same except its not costainly monitoring the water level and filling so salinty is not exact all the time, but ive been doing like this all the time, i guess if you have sps, please any advice would help