Ive been floating around here for a few months after i purchased a used 55g and stand all for $150. I leak tested it and everything for a week and after that cycled it. It had been up and running fully for a month when all of a sudden it decide to spring a leak sometime around 11:30 at night. In the chaos of trying to empty the tank, cause it was a pretty substantial leak, i moved all my fishes for the time being into a rubber maid container of about 25g. I had set it up all perfectly with the heater and the filter and tried to make it feel like a home for the time being, but with being rushed during the late hours of the night I forgot one crucial detail that has cost me dearly. i had forgotten to put the end of the filter thing back on that keeps the fish out of it and during the night my peacock eel (Moses) found his way up there and you can guess what happened after that. it has been a rough couple of days.
Welcome to AA! Sorry to hear about the loss of your eel. If you have not fixed the leak yet and it is just a silicone issue, resealing tanks is a pretty easy job, but, you have to remove all old silicone which is a pain.