i used to breed guppies but got out of it becuase it was simply takeing up too much time and space! i used simple cheap 10 gallon and 1 gallon tanks i never used a heater or filters and my guppies were very hardy BUT i did do weekly and daily water changes depending on the tank. some people prefere bare bottomed personally i had the hardest time keep this clean in the fry and juvy tanks i was litterly emptying the tank everyday and scrubbing it with a brush only to have it be murky and grey the second i refilled it with clean water.
i had all my store bought guppies in one 20 gallon tank with no filter or heater just an air stone (my room however was kept in the 80s for my other pets all year round) and i would do about 70 percent water changes weekly. people have there own opinions about water changes some say not to do large oens some say its ok ive never lost a fish from large water changes and ended up with very very hardy fish so i think it all depends on your what your comfortable doing. when a female was ready to drop i would move her into a heavily heavily planted half gallon bowl with an air stone once i seen the fry swimming around she was put right back into the main 20 gallon since i had about 10 females i would always have about 3 bowls and air stones/pumps.
i would keep the fry in this one gallon bowl for about a week doing daily water changes and feeding heavily about 9 times per day before they would be sexed and seperated males in one ten gallon tank with a bubble wand females in another 10 gallon tank with a bubble wand i kept my ten gallons empty other then gravel simply becuase it seemed when the tank was bare they were freindlier didnt hide or school makeing it easyier for me to catch them when i needed to. these tanks had a 50 percent water change every 2 days and 70 percent every other week while they are still being fed about 9 times perday
later on however i did opt to use homemade sponge filters on both these tanksuseing a cheap 5-10 gallon filter from
wal-mart and use some clean store bought foam and put it on the intake of the filter the bacteria colonies will build up quick in that sponge so i reccomend just rinsing it out once the water flow slows way down. as for the fry i could not tell at a week if they were males or females i would leave in teh bowl for another week or two.
and yes you CAN tell males from females after a week the females will have a grvid spot the males will not fry your unsire of may have tiny tiny gravid spots or what looks like a bigger tummy but no gravid spot just leave those ones be for another week or two.
now once my females were about 2-3 months of age i would pick out 2 of my favorites i looked for the largest or most colorful ones take two of them and place them with a male i liked or i thought would go well with and put them in a 2-5 gallon tank with an air stone and some plants these tanks would get about 70 percent water change weekly. after i got about oh 2 or 3 batches from those females i would put them in the main tank with the other guppies or sell them. i also never had lids for my tanks yes guppies will jump out but thats usually only nervous fish which is part of the reason that i kept my fry in empty tanks never had issues with them jumping out.
heres a few pictures of some of my guppies