guppies newbie here. received a pair of blue tux from a friend, and another 2 male satin pearl like guppies.
then i introduced another 2 x "<" tail guppies...

then this morning, all except the female blue tux died
lost i felt most is the male blue tux - the color was so nice

I learned the hard way i.e. all fish died within 1st 3-5 days of new water...

High ammonium & nitrate caused the death... means the biological cycle not complete yet/ established. Naturally, it takes days to weeks or you could expedite it using Sera brand bacteria - cost you RM22 for 100 ml. It works for me. Be careful, the ammonium and nitrate increase faster in smaller tank

I still learning on CO2 setup, in the mean time I use AZOO Carbon Plus which costly in the long run (I plan to use CO2 by end of the year)

LFS (adjacent to a electrical shop) got good grade soil, ADA soil and japanese soil cost around RM12 - RM20 ++ per kg.

2 ft above I use tube to suck out 1/3 of the water from base.
Small tank just scoop out 1/2 of the water, then I use "TensionGon" to neutralise the new water (should apply before adding new water)

perhaps overfed but ammonium does build faster in small aquarium setup compared to bigger size aquarium... and I worry less if they survive after 3 days - now got fries but lessen coz eaten by my cardinal tetras

queen avenue pudu (jln peel) got guppy breeder with variety of strands. price per pair could depends coz sumtime could match those prices by sarawak breeder in mudah.com

check past replies. this got to do with nitrite cycle... you can make the cycle faster by adding the solution (x remember the name) or let the aquarium established and complete the cycle in a week or two, then only add in fish

Crowded. Also, when u got fries, those fries gonna be eaten coz no space to run or hide. Maybe u need to add another tank