I use a 5 gallon bucket as my tank. It is made of thick HDPE plastic. I buried it most of the way because I found that my concrete pad got so hot in the direct sun it was cooking my bleach in the bucket. My bucket is now still in direct sunlight all day with zero shade. Ive decided to use 8.25% bleach for it's longer stability, and I normally only put 2 gallons in my bucket at a time. I feed about a quart a day to my pool, so 2 gallons lasts me plenty long enough, and even in 100 degree heat, should stay close enough to 8.25% to keep me happy.
So my biggest piece of advice is do not set your container on the concrete pad. Providing shade is up to you.