hello- (sorry this is so long...)
I bought a 20 gallon Marineland aquarium kit at PetSmart. It came with the Penguin 150 biowheel powered filter, heater, LED
day/night hood, etc. I decorated it with plants and decor only from the fish section, plus 20 lb of the natural colored gravel. I waited a few days after filling the tank before adding fish. I didn't really know about a fishless cycle at the time, so I did a fish-in cycle. After confirming my water had no ammonia, and good pH and temp about 80*, I added 4 platies on Feb 11th. I was feeding them small amounts twice a day, and testing using the strips for the first couple of weeks. Ammonia spiked, so I did some small water changes (10-20%) every other day, the ammonia would decrease, but rose again quickly, so I started doing bigger water changes (40-50%). Always the ammonia would go down, but no nitrates or nitrates.
After a couple of weeks, I bought the API water titration kit, and a gravel vacuum for the water changes. I was still doing pwc
frequently, 2-3x per week. With the test kit, still no nitrates or nitrites, and ammonia never goes all the way to zero. Hovers around .25 ppm
according to the API color chart. Also, around this time I switched from Tetra AquaSafe to Prime for my water conditioner. Also, at around the 2 week mark, my orange Mickey Platy (Garnet) died. He never really adjusted well, always hiding, didn't eat much.
Petsmart recommended I reduce the frequency of my water changes, so I tried that (sometime in mid-March). Ammonia seemed to stay relatively low, although never 0. I thought maybe I had just missed the tank cycling and that maybe Prime was giving me high ammonia readings, so I started thinking about adding a few more fish.
April 7 (8 weeks since my first fish were introduced), I added 3 new platies. So this brought the total fish in my aquarium to 6. After a brief acclimation period for old fish and new, they started getting along pretty well. They seemed active and always hungry and eating well, so I figured things were going well. I continued the testing about every other day (plus my extra ammonia monitor hangs on the inside of the tank in case of emergency spikes.
April 21, Thinking about adding 2 more fish. but then April 23, I woke up to find that my favorite fish, a sunburst platy "SunDevil" was dead. I tested the water, everything seemed the same as always. A little bit of ammonia, no nitrates or nitrites. She was one of the originals, so she was 10 weeks in my tank. No physical signs of illness or stress.
Lastly, I tested my home tap water, no ammonia, nitrates or nitrites. Only chlorine is used, not cloramines. pH, about 7.5.
Let me know if I am missing any details, or if there are any new ideas out there. I feel like I have read so much information, but I must be missing something!