If you are doing everything right they do it simply because they can. The basic rules are :- 1 inch of fish needs at least 1 gallon of water (an active Guppy needs at least 3 gallons but 10 gallons is better for a couple). :- Every tank needs a permanently running cycled filter. :- Every tank needs at least 50% of its water replaced every week.. A Guppy likes a pH of around 7 to 7.2 and a temperature of around 70F to 75F. They should be fed as much as they can eat in 15 minutes every morning and evening.
In my experience, if they're frantically swimming up and down, they're stressed- maybe sick.
yes
up and down
Up and down. All marine mammals swim with vertical motions, and fish swim with horizontal motions.
up and down
they flap it up and down and make splashes
Up and down not so sure
they are stressed or sick
just for the crack of it?
Sorry to say, But he is dying. The nipped fins might be because he was attacked by another fish. And since that happened he probably can't swim as well.
swim bladder
Guppys are special fishes that DO NOT lay eggs. They give birth to young.
No. If you exclude the length of the tail (caudal) fin in some male guppys, under normal circumstances, female guppys grow to around double the size of male guppys