I think you are good to go. If both walls are load bearing and your walkway is only about 8-10ft. Do a water test and fill up your tank and run it for a week. Use a leveler and see if there is a big difference between empty tank vs full tank.
Side note, how is that light rail secured to the tank's eurobrace? The legs looks a bit narrow. I'd be afraid of it tipping over.
Thank you. So, today was the day to install the suggested solution. I bought the two jacks, the 5-foot wood piece, 4 x 4, and two concrete feet with wood caps. It wasn't easy to get to the area due to various pipes on the way, which reduced the headspace to 8-10 inches (from 19 total) and required the concrete feet to lift above those pipes while lying on the floor. A nice test of resilience

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However, the bad news is that while all was finally set, the two 1 feet jacks were too high when sitting on the concrete feet. So we could not finish the job. The good news was, however, that another concrete wall was running perpendicular to the other walls roughly through the middle of the tank. So, even with the correct size jacks, I could not have the wood piece below the tank because this perpendicular wall would block it. I assume this concludes this little DIY session, which was fun, to say the least (…).
Regarding, the light rail: Yes, I have not been super happy with it. It would tip over if you push against the light on top, not if you hit the stand below, though (it would just slide away). So I have discussed this with Daniel, the owner of ReefiLabs, and he will build/3d print much wider feet now, hopefully solving the problem (as per the picture). And he will only charge for shipping, even though I offered to pay for these. I can only say the very best about him.