Ive been feeding them flake food once a day (to prevent overfeeding because the tank is relatively new, which I'll get to in a minute). Im pretty sure I dont overfeed, as all the food is gone in 30 to 45 seconds (i am underfeeding?). I have a 20 gallon tank (~75 liters) with smooth black gravel as a substrate. The 4 platys share it with 5 danios (which I used to cycle the tank)a pair of corys, and 2 ghost shrimp.
Water parameters:
The ammonia is trace (ie. <.25ppm. is this because I added some fish recently? they were zero last week), nitrites are zero and nitrates are ~20ppm (a little less actually). The numbers really make no sense, as the ammonia never really spiked when i was cycling it (or at least thought i was cycling) and the nitrates seem low. They stayed at .25ppm. This is my first fish tank, so I did a lot of reading and researching on aquariums- particularly on how to start a tank. I set it up 3 weeks from last friday. Is it possible that the tank never cycled, or is not fully cycled yet?