A "no touch" way to monitor fluid levels is to use a pressure transducer. Freescale makes one that is inexpensive that is 1 to 1.5 psi which can measure several feet of fluid depth.
With the tank empty or if there is a valve that you can close, you put a t-piece in your draw tube that comes off at or near the bottom somewhere to the side of the tank. To the t-piece attache a piece of pipe and run it straight up to a level that is a few inches above the top of the tank. You put a nipple on the top of that tube and connect the transducer with a short piece of tubing. Vacuum tubing from the auto part store works well for this. Then when fluid is put in the tank, it will partially fill the tube compressing the air in the tube and raising the pressure in the tube. The pressure transducer will read the pressure and report a value between .2 and 4.8v as the pressure increases. You fill the tank and note the pressure when full. Then it is just a linear scale between that number and .2 from full to empty.
You can use an Elk zone to measure the voltage off of that transducer and have it send you an email when it gets below some number.
Total cost for a project like this probably is in the $35 range. The transducer is about $20 as a one-off purchase including shipping from digi-key, and the iron pipe t-piece, a few feet of pipe, a nipple, and vacuum tube should cost but another $10 or $20.
I've seen people describe using ultrasound to measure the distance to the fluid from a fixed point (like the fill port). Also a float of some sort would work. Probably both of those cost more, and may or may not be more work depending on if you can buy a pre-made purpose built device.