In my neighborhood a concrete slab is poured, then concrete blocks are used for the sides. Concrete is used instead of plaster. They are generally small, 8' by 10'. The bottom is covered with dirt, water is added and allowed to sit for two weeks until the proper bacteria is formed at which time the fish are added. They may or may not add plants. The neighbor nearest me has ten of them, two rows of 5 each. Her's are fitted with drains and overflows for the rain and she keeps them topped up with well water. Some here are used for aquaculture, a truck comes by and sells you umpteen baby cats and returns in 4 months and harvests them, you are paid by th kilo. The majority are for personnal use to raise food. The only washing the tanks received is from the rain. The algae bloom here can be awesome, but the cats seem to survive.
