I didn't really know what to title this thread, this is more of a post trauma question, as everything is fine now but have no idea what happened last night. My google searches have been rather fruitless.
50 gallon tank, well established low tech, with lots of large anubias, Fissidens fontanus, and various crypts. I had everything pretty perfect for the past 4 years, 20% water changes monthly, bi annual filter cleanout, light cycle, etc.... I haven't lost a single fish in 3 years, but my crypts have been slowly dying off as i haven't changed the substrate in over 4 years, and due to life stresses not to do with my tank i had a large BBA infection sneak up on me.
Saturday morning I finally decided to spend a couple hours and get everything fixed up again. Pulled everything out of the tank (plants, rocks, wood etc) Brought the water level in the tank down to 25% (fish still in it) and delicately removed about half of the old florite and replaced it with new. Sprayed wood, Fissidens fontanus, anubias, and rocks with hydrogen peroxide (50% Hp, 50% water) solution to kill off the BBA, trimmed roots on all plants, re-planted and re installed all plants wood, rocks etc.... Then refilled the tank with (50%ish new water 50% old water) I used proper de-clorination, and dosed with my regular dosing of phosphates, minerals, etc...
Skip ahead to last night (36ish hours later). Prior to the lights going off all the fish were happy as clams, BBA was turning a satisfying magenta color, water was nice and clear, things looked just fine. I am then awoken at around 2:00 am (6 hours after lights out) to a thrashing noise, and turn on the lights to see the worst cloudy murk i have ever witnessed in any of my tanks. My angels are dead, all my schooling fish (various rasboras and minnows) are dead or gulping for air desperately at the surface, and my cory's and otto's are rushing to the surface and almost jumping out every few minutes. I added an air stone and checked Amonia, Nitrate, nitrite, and all are 0 or below .25. After frantic google searching I lowered the water level to get additional surface agitation, turned the light on hoping the plants will help in the process, pulled the dead bodies out and went back to bed.
I woke up at 7 this morning (5 hours later) the tank is mostly clear, cory's, otto's, and one very sad looking lamp eye are all acting like nothing ever happened. Re-checked the water and everything is still below 20ppm.
I think the crisis is over but I really want to know what the hell happened so I don't do it again? I found it particularly strange that all the bottom feeders and cleaner fish survived and my "robust" fish like White cloud minnows died off. I really would have expected my Otto's to see the toilet first!
TLDR: Established tank, 50% water change, 50% substrate replaced and BBA nuke, fine for 2 days, turn on lights, fish dead, tank cloudy, 5 hours later like nothing happened.
50 gallon tank, well established low tech, with lots of large anubias, Fissidens fontanus, and various crypts. I had everything pretty perfect for the past 4 years, 20% water changes monthly, bi annual filter cleanout, light cycle, etc.... I haven't lost a single fish in 3 years, but my crypts have been slowly dying off as i haven't changed the substrate in over 4 years, and due to life stresses not to do with my tank i had a large BBA infection sneak up on me.
Saturday morning I finally decided to spend a couple hours and get everything fixed up again. Pulled everything out of the tank (plants, rocks, wood etc) Brought the water level in the tank down to 25% (fish still in it) and delicately removed about half of the old florite and replaced it with new. Sprayed wood, Fissidens fontanus, anubias, and rocks with hydrogen peroxide (50% Hp, 50% water) solution to kill off the BBA, trimmed roots on all plants, re-planted and re installed all plants wood, rocks etc.... Then refilled the tank with (50%ish new water 50% old water) I used proper de-clorination, and dosed with my regular dosing of phosphates, minerals, etc...
Skip ahead to last night (36ish hours later). Prior to the lights going off all the fish were happy as clams, BBA was turning a satisfying magenta color, water was nice and clear, things looked just fine. I am then awoken at around 2:00 am (6 hours after lights out) to a thrashing noise, and turn on the lights to see the worst cloudy murk i have ever witnessed in any of my tanks. My angels are dead, all my schooling fish (various rasboras and minnows) are dead or gulping for air desperately at the surface, and my cory's and otto's are rushing to the surface and almost jumping out every few minutes. I added an air stone and checked Amonia, Nitrate, nitrite, and all are 0 or below .25. After frantic google searching I lowered the water level to get additional surface agitation, turned the light on hoping the plants will help in the process, pulled the dead bodies out and went back to bed.
I woke up at 7 this morning (5 hours later) the tank is mostly clear, cory's, otto's, and one very sad looking lamp eye are all acting like nothing ever happened. Re-checked the water and everything is still below 20ppm.
I think the crisis is over but I really want to know what the hell happened so I don't do it again? I found it particularly strange that all the bottom feeders and cleaner fish survived and my "robust" fish like White cloud minnows died off. I really would have expected my Otto's to see the toilet first!
TLDR: Established tank, 50% water change, 50% substrate replaced and BBA nuke, fine for 2 days, turn on lights, fish dead, tank cloudy, 5 hours later like nothing happened.