As someone who has over 800 gallons in aquariums between three tanks in his house, I'll say structural support is not as important as people make it out to be (ask an actual structural enginer). Anything up to 120 or so is just fine hanging out on a floor without extra support.

Also steel is completely unnecessary unless you're doing something wild like that guy in NYC with a 17,000 gallon home aquarium. If you're just throwing a 200 gallon or so on a second floor, an enginer might not care at all if its across the joists or has a wall below it, but even if its completely open below, the "support" might just be a joist of a different design, or an inch thicker or one extra joist. Steel is really not nessecary

But big tanks do need extra support. This is a relevant thing to post in case someone is thinking about scaling it up.

The Pfizer building in NYC almost collapsed after they tried to build a swimming pool on the roof. This happens semi-regularly when building owners ignore, or don't consult, engineers about rooftop swimming pools. Every owner wants one and doesn't want to be told no.

I looked it up, you are looking at 160lbs (75kg).