male neon tetras have a straight blue line, females have a bend in the blue line.
the 3rd fish down (on left) is skinny and has gill flukes or intestinal worms or both.
See section 3 of the following link for treating them.
Fish do a stringy white poop for several reasons. 1) Internal Bacterial Infections causes the fish to stop eating, swell up like a balloon, breath heavily at the surface or near a filter outlet, do stringy white poop, and die within 24-48 hours of showing these symptoms. This cannot normally be...
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