First off, I'm so sorry! No words can begin to describe what you're going through! I've been there. My home of 8 years burned down. Was a total loss (this April was the 10 year anniversary). I was in a town home, 4 other families were impacted by the fire and to make it worse like you, the fire started in my unit.
My suspicion is that it was possibly tank related, I had built a new canopy for my 125. I had just finished staining it and was waiting for it to dry in between coats. I was doing it in the winter in my living room (windows open). I threw the used rags in the garbage can. They possibly ignited.
The fire marshall, says it was possibly the 1 year old Fridgerater. The heat around the fridge was so hot that the fridge fell through the floor (crawl space) and all that was left of the fridge was the metal compressor, the frame, the door, everything literally incinerated. It could have been the fridge. I have no idea.
Fire happens, doesn't matter if it was aquarium related, a new refrigerator, an animal chewed through electrical wires in the crawl space (could have been the case, had many issues with critters).
The hard part for you, is it's hard to say, did the fire start as a result of something electrical with the tank or did something else around the tank start on fire? What if the outlets were just faulty and triggered the fire? Would the fire have happened without the aquarium? It's entirely possible!
In short, don't blame yourself. There is no "I" in blame. I know it's hard, but, allow yourself to grieve, mourn the loss of what was, and give yourself permission to grieve. This was not your fault. You had more safety in place than most of us reefers. Even if it was tank related, (which I still question), You had so much redundancy and safety in place! My cords are a complete cluster and mess. Yet, I make sure they're as far away from water as possible and have drip loops, etc. I'm paranoid on safety, but there's only so much one can do.
There's the emotional side, it's tough, it's strange to be homeless, and have no possessions. It's also a time to reflect and rethink one's contributions to society and what one wants to accomplish in life. We get so material at times, that we forget that without possessions who are we?
Lastly, the tactical insurance side of things. I was so overwhelmed by the fire, I found it difficult to think straight on how to claim all the stuff I had. I am an honest person and wanted to only claim what I had. If I had to do it all over again. (I pray I never have to and no one else ever has to). Claim as much as you can for contents. My insurance company had me list everything I thought I had (did not require proof at all, it was a total loss). And then the insurance company went through and assigned used market value to everything and then wrote a check to me out of the contents part of my plan.
Then, if I went out and bought a replacement of that product, it needed to be close to quality and brand of the original, I could submit a receipt for the difference between the market and new replacement value. There's just some things one doesn't replace.
Aquarium related stuff, insurance doesn't usually cover living things. So, what I did right was claiming, custom coral decorations. I didn't try to claim the fish. Then, for the replacement aquarium, stand, and sump, find what you would like and submit those as what you had. Unless your insurance (and / or state) requires you to go find receipts for original stuff (mine did not). For things that I didn't have documented they just took my word on replacement. This can differ by insurance company though.
I left money on the table in my contents mainly because I was single at the time (was a marital home for 8 years), but, I didn't realize how insurance worked and was too honest.
I met other families that were at the victom of a fire at the time, and they were stating they had 5 ipads, 5 computers, and 5 -10 of everything. I didn't feel that was right either. As a result, I actually probably did lose some financial impact despite my efforts to reclaim what I had lost.
Feel free to DM me if you need to just chat, or have questions. This is an overwhelming time and I wished I would have had more support than I had at the time. I lived out of a hotel for 2 months while I attempted to put my life back together. I'm in a much better place now and I'm here to tell you there is hope! Despite everything there is hope, you have you and your family, and right now that's all that matters!