I have been gradually adding fish to my cycled 24gallon tank for the last few months. I started with a few danios and a BN Pleco, now I have 7 danios (2 zebra, 2 leopard, 3 pearl), 5 neon tetra, albino BN Pleco, and 4 guppies.
All was fine in my tank until 3 weeks ago when I added a very small...