Swollen betta

Question
Hello,
My betta start swelling from the bottom with the raised scale. Nippy eats well,swims around,fight with platies and yes nippy stops scaring other fishes by raising gills but I think that nippy is too little and platies they are fully grown. Nippy's swelled abdomen makes me worried help Please

Answer
Arsalan,
If Nippy's scales are raised, it sounds like Dropsy. Dropsy is not a disease, but a symptom to other diseases.  Unfortunately, dropsy is almost always fatal.
Immediately change at least a quarter of the water in the aquarium. The water must be treated as mentioned in the step that follows and this water must not be re-used anywhere later on.

Place the diseased fish into a quarantine tank. You need to treat the rest of the 'unaffected' fish too - just in case.

Administer a prescribed antibiotic to arrest growth of the infection. Suitable medicines are Maracyn, Kanacyn, Neomycin, or tetracycline drugs and anti fungicides for treating the tank water etc.

A medicated bath must be given to the fish at least two times a day with methylene blue, salt, Epsom salt, and electrolyte balancing salts to ensure removal of fluids from the fish and to keep electrolytes in balance. The proportion of medicines in this bath is clearly mentioned on the labels and one can still confirm the procedure either with the pet shop or the vast library base on the Internet.