Invertebrates for coldwater?

i bought one of my tanks and i didnt set up the tank for a week and saw little mts's in.
filled with water. and there was hundreds alive. tiny tho. so crazy 1 week no water in sun.
 
i've had some ramshorns in my 75 for a while before i added a heater and they laid lots of eggs. i see at LEAST 20 eggs above my sand, but even underneath i can see a LOT more eggs attached the the glass that at first i thought was air bubbles. anyways, they were fine in the cold temp of my tank (which was around 62 degrees)
 
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