I went ahead and used 100% DT water and immediately put a heater in it to maintain the temp, then had to take out all of my LR
to catch the fish. That way I didn't have to wait on the temp to adjust. Also you might consider getting an aquarium rather than the rubbermaid. The sides of those bins tend to buckle under the weight of the water. I'm curing some DIY live rock in one right now and it's so warped I can't even fit the top on it anymore. Not to mention it'll be really hard to observe your fish during treatment in the rubbermaid.