First the details on my tank setup. I have a ten gallon plastic tank. I use a UV lamp and basking light for my turtles. I have a filter and a 5W submersible heater. They have one fake plant and several rocks in the container which are used for basking. I feed the turtles, twice a day, three pellets of ReptoMin Baby food. I have two 3-month-old RES babies. Today I cleaned their environment, emptying all the water from the aquarium and used and aquarium brush to scrub the sides and bottom of the tank. I also used a brush (dedicated to aquarium use) on all the rocks, and I rinsed the leaves of the fake plant. I always use less than a teaspoon of bleach to clean the tank, no detergents, and rinse thoroughly with lots of water, until I can't smell the bleach any more. I do the same process weekly. While I clean the tank, the turtles are kept in a carrier that was bought from the pet store. After refilling the tank today, I put the filter and heater back in the tank and turned on the lights. I keep the water at 79 F. The fresh water I put in the tank comes straight form the tap (municipal, not well water) and is always warm (near body temperature) but never hot. The lights are clip on and attached to the side of the tank. At no time did the lamps ever touch or fall in the water and the cords were completely out of the water. I put the turtles back in the water. Immediately, the first turtle in the water began swimming frantically and bumped its nose on the rock. It swam to the side of the tank opposite the heater and began swimming in circles. The next turtle in the water did the same thing. Then, one of the turtles began diving up and down. It then did a backflip. (I have never seen this happen.) It swam to the basking rock and then dove off of the rock. The second turtle began to swim in a circle with its mouth completely open. The other turtle did the same. They both swam in circles with their mouths open. Then, simultaneously, both turtles stopped, splayed out and fell to the bottom of the tank, next to each other. This activity took place in under 5 minutes. This occurred around 4 p.m.. I checked on the turtles periodically, and they did not move. (I assumed that they were sleeping, as this is the usual sleep position for my turtles). At 8 p.m., I was alarmed that there was no change so I took the turtles to an emergency avian and exotic animal veterinarian. The turtles had not moved after taking them out of the water, nor on the ride to the vet. The doctor listened for 20 minutes to both turtles with a stethoscope for a heartbeat, but did not find one. He opened the mouth of the larger turtle. The inside of the mouth was grayish-white and fluid was coming up from the lungs. He said that there was also food in the lungs. The other turtle had fluid coming out of its nose. The turtles were determined to be dead. There was no skin discoloration on the outside skin or shell of either turtle. Both appeared to be simply frozen in a pose. What would have caused the turtles sudden death? I wonder if the turtles may have been electrocuted? When I touched the water surface to pick up the turtles, I received a small static shock, but there was a lot of static electricity in my apartment already.