Hi Guys, I need some help please. Here are the stats.
Fresh water tropical 190L tank, PH 7.8 (water from tap 7.8), ammonia 0, Nitrates & nitrites 0, Freshwater, set up for 1.5yrs, I have 7 x rummynose tetra, 4 x emperior tetra, 10 x zebra danio, 2 x silver shark (tiny), 6 x harliquin, 4 x platy, 3 x bristlenose plecs, tank temp at 26 deg, live plants & bog wood, Fluval 405 external filter, bubble hose running, lights on from 5pm till 11pm daily, fortnightly water changes of 26litres per change.
Heres what happened.
I have had my tank setp up now for about 1.5yrs. Haven't had any problems with it for the last 4 months. Went to shop on Saturday and purchased 4 x platy, 7 x zebra danios. When I got home, I did my normal fortnightly 26 litre water change before I put the new fish in. Put them in the tank. Everything looking good. On Wednesday night I noticed one of the male Emperior Tetras swimming by himself which isn't normal. I put him in a small guppy breeding tank so the others didn't pick on him. He was floating the next morning. Everyone else in tank looked fine. Checked them all that night (Thursday) before bed and all looked good. This morning (Friday) my Dwarf Rainbow was dead floating on the surface. When I looked at the others, 1 male and 1 femal emperior tetra were swimming by themselves with their heads a lot lower than normal (tails up), and there is a slight loss of colour. I put a dose of Formalin in (3mls per 20 l). After work today I did a 32L water change and added Aquarium Salt (1 tablespoon per 20L).
Tomorrow I was going to put another full dose of Formalin in, 2nd day nothing, 3rd day water change, 4th day dose etc.
The fish that have died so far have died very quickly and there is NO sign of any disease etc in the tank.
What do you suggest?