i made the mistake of adding fish too fast on my first community tank. lost a few tetras and felt terrible. now i wait for 0 ammonia and 0 nitrite even if the bottle says you can add fish in 24 hours.
for a 20g i would do like 6 tetras max to start, then corys later. corys are messy for their size so dont go crazy. platties are hardy too if you want something a little bigger.
good call getting the test kit early. that saved me on my 29g.
