I've had a 20gal fully planted tank setup for 5 months now, and the tank spent its first 3 months with no fish. I found its easier to just worry about the plants and getting algae under control before adding fish to the equation. About a month ago I started stocking with algae eaters and added 4 otos first, then a week later 10 amano shrimp. On Saturday I found some really beautiful long finned zebra danios and put 6 of them into my tank. Monday night my tank was crystal clear and everything seemed great. By Tuesday night the tank had turned a translucent milk color and smelled like sulfur. All my shrimp died by the time I came home from work and noticed the problem. I immediately did back to back 50% waterchanges for the last 2 days, and while the tank is starting to look a little better, it smells to high hell still. Is this just a bloom of bacteria, and will it go away on its own? Any ideas as to the cause? The tank utilizes pressurized C02, EI dosing, 37W of PC lights and a Rena XP3 canister filter with lots of filter floss. Any advice? I'm hoping I can salvage the situation, only 4 danios and 3 otos remain.