what is the sand for? perlite/vermiculite was used as it holds moisture really well. if you're soaking it with so much water that you need a light diffuser, then the purpose it was used for isn't there anymore. I also use light grids. the first year I used perlite with the grids. now after some thought, I now zip-tie pvc tubing to the light grid. the pvc is about 1 inch in diameter holding the grid up out of the water. the only thing that the perlite did for me was when I take the eggs out to check on them. the perlite prevented splashing of the water (moving the egg tub). without the perlite, I don't have a problem with the eggs getting wet. and if you do splash, and the eggs do get wet. they will be ok. it's the eggs being constantly wet that causes problems.

thermostats. this is the most important piece of equipment you have for this hobby. why go cheap? if you can't afford about a 130 dollar thermostat, then you should get a hamster instead. haven't you read about all the fires? and those breeders were using good equipment! most likely why spyder robotics (manufactures the herpstat) came out with their new line of thermostats that has more safety features to help prevent this. heat tape, heat cable ect.. was used for many years to help keep water pipes from freezing in the winter time. Trailers with the air space under them has a big problem with this. many trailers burnt to the ground cause of heat tape. if you don't buy a quality thermostat for your reptiles, buy it for the added safety for your family. one thing I've learned in life, you pretty much get what you pay for.

and the 500r, the one I had was junk, I wouldn't even resell it at a reptile show. I threw it away. hope that answers you question.