The Silver Dollar Fish (Metynnis argenteus) is a popular freshwater fish known for its round, flat body resembling a coin. When discussing a “thick bar” variant, you may be referring to one of the species or morphs of the genus Metynnis, such as the Black-Barred Silver Dollar (Metynnis fasciatus), which features prominent vertical black bars on its body.
 
Here are some key features of the thick bar Silver Dollar Fish:
    1.    Appearance:
    •    Round, silver body with bold vertical black bars (thick stripes).
    •    Often slightly reflective, giving it a metallic sheen.
    •    Can grow up to 6-8 inches (15-20 cm) in diameter.
    2.    Behavior:
    •    Peaceful, schooling fish.
    •    Prefers to be in groups of 5 or more.
    •    Active swimmers, requiring ample space.
    3.    Habitat:
    •    Native to South America, particularly in slow-moving rivers and streams.
    •    Prefers warm water (75-82°F or 24-28°C) with a slightly acidic to neutral pH (6.0-7.5).
    4.    Diet:
    •    Omnivorous but leans towards being herbivorous.
    •    Enjoys leafy vegetables like spinach or lettuce, along with algae and pellets.
    5.    Tank Requirements:
    •    A minimum tank size of 75 gallons or more is recommended for a small group.
    •    Provide plants, but be aware they may nibble on them.
    •    A secure lid is essential as they are known to jump.
 
These fish are ideal for peaceful community tanks but should not be kept with very small fish, as they may inadvertently harm or eat them. If you meant a specific variant or care requirement, feel free to clarify!