Water storage ideas/suggestions?

[Alberta-newb]

Hi everyone, I'm still in the process of my 120 in the wall build and am looking for suggestions/ideas on water storage. I have a RO/DI unit on its way and I'm wondering what you all suggest. I have a closet adjacent to the tank for my hardware and I'm looking at a 30 gal RV storage tank to put in there.

I already have a 5 gal hopper bottom I bought from the same place that I mounted above the tank to gravity feed my ATO. This will be filled manually with RO water and goes to a float valve in the sump.

I was planning on two storage tanks, but reconsidering to conserve space. Is it better to have storage for just RO or do some of you keep pre-mix SW for water changes? Which keeps better? The tank is made in black so algae growth should be less of a problem and I was thinking about permanently installing a pump/powerhead and a heater in it. I just want to avoid too much work and mess with buckets.

Thanks for any ideas.

Francis "Alberta "