I've had my sorority tank for almost 2 months with no problems except a defect with the tank which made the pump buzz loud until I exchanged the tank on Tuesday.
It's an evolve 8 gallon tank with 6(now 5) Halfmoon females an Otto catfish a host shrimp and 2(now 1) African dwarf frog. I drained about 4 gallons of water from the old tank and used it in the new tank. Yes..I rinsed the gravel out as It was just sitting in a bucket while I did the exchange and of course the new tank has a brand new filter with no beneficial bacteria..I also did about a 1/4 water change yesterday. Every thing was fine until I noticed this morning every one was lethargic, 1 girl was dead, 1 looks like she is dying and a dead frog which I just got the other day. The frog kept going back in the compartment behind the pump and I don't know if he damaged himself as there's a space where they can't go up for air back there and I already lost 1 frog like that so I don't know if that's what killed him the water or he was sick when I got him. My other ADF is fine.
I took evrryone out and placed them in a 5 gallon half full with some aged water, aquarium salt and water conditioner. I just rinsed everything out in the tank again and started over...I took a sample from the old water and I'm going to go to petco later to have it checked. Even though I used half of the old water is the brand new filter and clean gravel the culprit here?