Male Molly Losing Weight Fast

[blueline-uk]

my male molly has lost weighy rapidly he is in a community fish tank of 30 litres he is active with the female molly and eats well im worried as he has gone half the size of what he used to be ... i feed 2 daily and also give bloodworm as treats every so often . the only thing that has changed within the tank is that i have had to put in a birthing net as my female guppy has had 2 fry

 

[WILDER]

Losing weight fast can be due to fish tb, internal parasites to flukes.
What colour is the poo when the fish goes to the toilet.
Is the anus red and inflamed.