I have 4 10 gal tanks.
#1 - Maternity Ward - 2 very pregnant marigold lyretail swordtails
#2 - Cory fry - 5 newly hatched paleatus corys
#3 - Swordie fry - about 3 dozen black swordtail fry, 1 marigold swordtail fry,
2 orange swordtail fry and 5 or 6 neon swordtail fry. These guys would
normally be split between 2 tanks but the corys have borrowed one of the
swordie's tanks. The cory cleanup crew - 8 paleatus corys soon to be
split up and some will move back to the 75 gallon tank.
#4 - Spawning tank - 58 freshly spawned cory eggs. Once these guys hatch they
will hopefully be joining the other 5 corys so the swordies can have this tank
back.
Under normal circumstances I usually have 1 tank set up as a maternity ward, 1 tank for swordie fry, 1 tank for quarentine fish and the 4th tank available for whatever might be needed.