Tank Entry

So I have a 10g tank, in my soon to be fish room, with some old substright, a bio wheel backpack filter and a light. The tank temp is below 60 degrees and the salinity is at 1.023. The light stays on for about an hour a day and has some natural light for the rest of the day. It has been running like this for about a month.

The first few weeks there was no life at all. Then I saw some small snails moving around the sandbed. A few weeks later I found a small pure white aptaisa and ...

So I came home today, after a long day of shoveling snow, to find all of my fish dead. Don't know what the hell happened. My corals seem to be doing ok. Most of my zoos are open, my acans are fine and my shrimp is still alive for now. So I did a 5 gallon water change and turned up my skimmer. We will see what happens tomorrow. My lights just went out. What the hell......