I've done some reading up on these plastic storage containers. Most are made of plastic that is not "food" safe. Which for me, I'm not going to use it for this hobby.
I understand the cost of acrylic sumps aren't on the cheap side. But the cheap aquariums from pecto/walmart you know is 100% safe for our hobby. When investing hundreds/thousands of money into coral, why go cheap on things like a sump? I at the very least recommend you either find a cheap aquarium from petco/walmart, or buy a used one from craigslist for your sump needs.