Things about fish that amaze or amuse me

Livebearers can give birth (a month apart) several times from one mating. 
They save "sperm packets". 

Interesting, yet frustrating when the tank becomes overrun with fry.  I also got tired of finding fry in the bottom of an Aquaclear filter, (alive and kicking, thank you).

My solution has been to separate the boys from the girls, and keep them with tankmates who are happy to eat the fry (tetras, gouramis, angels).  Of the livebearers (guppies, platies, swords, and mollies) mollies are the least likely to eat their own fry.

Lories poop a lot, from the tiny ottocinclus to the
larger plecostomus.  Good circulation and filtration helps to sweep this into the filter, where regular maintenance keeps it at a minimum.

Fish can, should, and will eat a variety of food.

I'm always trying out new veggies.  Some blanched, some raw.  I leave them in for a few days, often there's nothing to remove.

Favs so far: green beans straight from the can, asparagus stems, steamed broccoli, blanched romaine lettuce.

Labryinth fish, such as bettas and gouramis, have a special organ that allows them to breath air. 

Interesting to watch them go up for a breath of fresh air.

Breeding: some fish are egglayers, some are livebearers.  Of the egglayers, some exhibit various levels of parental care, others have absolute disregard for the eggs.

Some lay their eggs in a neat fashion on a well-cleaned leaf and take care of them, others scatter them about and go on about life.

Sometimes the father takes care of the eggs, sometimes the mother, or even both parents.  Some cichlids are mouth-brooders, and keep the eggs and fry in their mouths for safekeeping.  Discus fry feed on the slime coat of their parents.

The breeding of fish in captivity can be both a joy, and a pain in the neck.