I am an old timer. We vacuumed the substrate, manually skimmed foam off the top of the water, and had very short term success with tanks. I can remember when we called them foam fractionators.
Back then the biggest obstacle in keeping a tank was high levels of nitrates. Then they introduced wet-dry/trickle filtration and other methods which accomplished nitrate reduction. So, then the issues of the day switched to denitrification. Thus the introduction of deep sand beds and live rocks. And the Berlin style instead of underground filters.
Now, we have denitrification methods that don't even require sand and rocks. But that's a whole other story and I'm not trying to write a book on the history of the reef aquarium.
It's a long story, but I had an 8" pipe running 20' up a pine tree for my crab shedding tanks back in the early
90's, but it wasn't called a protein skimmer. I was even published on that method and my findings were distributed up and down the east coast for other crab shedders.
Also had a full size septic tank full of ancient reef rocks for a sump, but we didn't call it that then either.
The biggest advancement back then was the use of live rocks and deep sand beds for denitrification in saltwater tanks.