This is my 20 Gallon back in 2005.
The large circle rock was DIY using Home Depot Sand and cement.
The tank met it's demise a few months later as my 3 year old poured all the food into the tank moments before we walked out the door.
Came back to a bright orange tank, murky as can be. Nothing survived.
Back in the day 2 x 250w metal halides and a 160w actinic tube. In m 30s there now in my 70s.
Tank was 130 UK gallons with a DIY sump, DIY ATU and skimmer. Sumps were a rare thing back in the early 80s. Powered by a Ehiem canister filter that had a turnover of just once every 3 hours.
I kept a magnifica nem with a trio of common clowns when all the "experts" said it was impossible to keep them more than a few weeks. I had it for many years before I broke the tank down and moved everything on.
This tank was very successful and featured in Practical Fishkeeping magazine.
I'll pitch in a few more. Same tank as post #19, but before it was a reef tank it housed a small Gray Smoothhound Shark (Mustelus californicus) for a while. (I used it as a lobster tank before that!)
And when he wasn't biting me, he loved his fresh crab snacks!;Drool
This is the only photo I could find of my tanks from when I was younger. I was already winding it down and only had a few fish left when I took this. This would have been summer 2006.