Swollen Betta!

[dylema]

HELP! We've just come home from work to find that our blue betta who was fine yesterday is looking swollen behind his face underneath his body (make sense?). He's looking quite pale too (the lump is particularly pale). What's wrong? What do we do?
We only have a four gallon tank, we had the betta and a single danio in it but put in two more danios a few days ago, they seem ok.

 

[cometcattle]

Are his scale beginning to "pine-cone"? It could be dropsy.

Also, is the tank filtered? It could also be nitrate poisoning. Sorry, but I think your tank is over-stocked.

Danios require at least a 10g tank, and that is even a bit small for them. They are very active swimmers, and need more space. Their constant movement is also stressing your betta.

Personally, I would return all the danios, or get them a larger tank.

The first thing I would do, is a good water change.

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