sorry to hear and I had your experiences at first until I started a planted tank.

So let me give you the short instructions.

empty tank

add 1" peat moss (from big bale not small packages)
add water to top of moss
level and clean
add 1" play sand
add water to top of sand
level and clean
add 1" pc select (or aquarium gravel)
add water to top of gravel
level and clean

(10g tank) add 4-6 bunches of anacharis, 4-6 vals, 4-6 small potted plants, and a single amazon sword.

fill tank to top pouring water over a saucer.

wait one week
add 1 male platy
wait 1 week with no food added
add 2 female plattys
start feeding 1 flake per day.


no filter, no air stone, no water changes just replace evaporative water with straight unteated tap water from a commonly used cold faucet.

Give that a try.

my .02

__________________
fw leiden since 1979, fo salt since 1979, mixed reef 55g 2002-2009. Strong emphasis on the tank taking care of itself. Balanced with plant life, no water changes, tap water, no filters in FW. Only dosing calcium, alk, mag in marine reef tanks. http://www.aquariumforum.com/f15/my-...ods-26410.html
recent tanks (till 2009) 7 years- 10g FW leiden 7 yrs, 55g mixed reef 7, 2 yrs, 20g FW leiden, 10 g fw leiden , 29g mixed reef, current tank 55g leiden