Over the years I have used Rubbermaid containers for fish things. My smaller buckets and bu large garbage cans are theirs. I also have their Sterlite and other containers I have used for fish things. However, I have only used these for temporary reasons. The containers where I have put fish did not have to be in used ofr more than a week or maybe 2. I fill the garbage cans for water changes and then pump from there into tanks. Again this is a shorter term situation.
I also batch my RO/Di water into a 20 gal. Rubbermaid trash can. I store some of it im 5 gal. Home Depot buckets and iot can be there for a few weeks. The water mostly goes into my Altum angel tank- if it were at all toxic the fish would show it.
While you are probably safe using this container, there will be drawbacks. Harder to make suction cups stay attached, worse isulated, hard to cover effectively. Also, plastic can tear easier.
I used a couple of Rubbermaids filled with water to put tank contents into when I have to collect pleco fry from breeding tanks. The babies can hide in decor, especially wood. So it all goes into a rubbermaid with an airstone and heater. I worry about how well the container might deal with the pressure pushing out, so I wrap the container, close to the top with duct tape. I may be paranoid, but it makes me feel safer. This would not look create in terms of how it looks.
Finally, I have used a Sterlite container to hold the entire contents of a tank including the filter etc. I needed to keep it all cycled and was adding ammonia to the container. it did fine thise way for a couple of weeks. I had to stop adding the ammonia becuase a friend pointed out there were fry in the box. Apparently, they came in as eggs on the plants from the tank which had been used to Q a batch of new fish.
I have never seen any signs that any of the fish which spent time in a Rubbermaid product suffered from that experience. All of my containers are dedicated solely for fish use.
