I use a 35g garbage pail for my rodi
reservoir and a 10g tank with a lid beside my main tank as my ATO reservoir. When it comes time for a water change I use a Rubbermaid bin that holds about 17-18g and heat/mix in that. I have another identical bin I drain the tank into so I can match levels of what comes out and what goes in. As for the ATO I stuck a chunk of eggcrate in my return chamber (nice tight wedge fit) and tie wrapped a chunk of PVC
pipe to it that and my ATO drains into that. Cuts down splashing and noise while keeping the hose out of the water to prevent syphon. I was using a maxijet to pump my ATO which was LOUD. Now I have an aqualifter and the only way to know it's working is by the water level dropping in the reservoir. I do have to clean out the 10g ATO reservoir every now and then as it will build up a clear slime over time.