OK, in the spirit of a true build thread, I'll do a walk-through posting info and pics up until now.
I had my first goldfish at age 7, was breeding bettas @ age 10, and got out of FW around age 12.
Fast-forward to age 25 I was breeding south american cichlids, mostly rainbows. This only lasted 1 year.
Another fast-forward brings us to 2010. My buddy had a 20g FW community tank and sparked my interest.
After my Wife agreed to me putting a 90g tank against that wall over there, I proceeded to bring home a brand new 125g with stand, PC lights, pumps etc etc.
After the discussion about the extra 2 feet died down, we covered the next few months spending thousands on fish, wood, cultured plants etc etc.
This was the FW tank in it's heyday. There were other iterations of plants etc completely covering the back wall and pretty much all the gravel, but this is the best one I can find for a FTS
After a year of collecting schools of common and very uncommon critters, we were up to over 120 inches of fish - in a 125g tank with 2 middle-of-the-road canister filters

Imagine seeing 20+ Head and Tail Light tetras shoaling, or 20 Cardinal tetras, or 5-6 Clown loaches. Or 12 different kinda rare plecos, breeding Japonica cats, breeding Angels, and the list was huge. We were addicted to say the least.
I had an under-gravel filter with 4 maxi-jets (including a 1200gph chiller circuit), but it wasn't enough to deal with the Nitrates. Probably had something to do with the pair of Rena XP3 filters that were only cleaned out every 2 weeks - 1 each every week. Good Nitrate factories those canister filters can be IMHO. Nevermind the massive fish load.
Weekly 50% WCs became the norm for many months.
After about a year of this, I started looking into a sump setup for filtration, but I'd need to punch a hole through the wall to my office behind the tank.
After a whole lot of research, I decided
if I'm gonna do all this extra work, I may as well go Salty. After all, every time the wife and I went looking for new fish, I'd have to steer her away from the SW guys. "But they are so much prettier" was always the reply ....
Well, she got what she wanted.
I sold off all the Live critters, and every piece of equipment that wasn't relevant to SW.
Then I jumped on the research train and spent the next 5 months reading and planning.
BTW, I wish all of you who are interested in doing the same, jump on a forum and read your brains out for 3-6 months.
But, ce la vie, so now the rest of us read numerous "rescue me and my dying critters" posts.
Anyway, no ranting
More to come ...