I have 10 in my 75 Gallon tank. Personally I wouldn’t go any smaller of a tank for these fish as they like to swim. A 4 foot tank or longer is a must.
I have had these 10 for about a year now and they range in size from about 2.5 inches to about 3.5 inches. When I bought them they were no bigger than an 1/1.5 inches.
They are very playful and curious. Even when my hands are in the tank they will come right up to me and literally want to be held (I haven’t done this yet as I am actually a little scared of them lol). They sleep upside down, right side up and everything in between.
They are probably the coolest fish I have wver owned.