The thing is, without the answers to all the questions it's very difficult to come up with any kind of diagnosis.
Despite you saying the aquarium is cycled we have no idea if this is really the case. For instance, many people come here and say their aquariums are cycled, when it turns they have no idea what cycling the aquarium means, and when you dig into the answers to the questions it turns out to be water quality issues caused by the aquarium not being cycled. If you tell us what the water parameters are, whether the aquarium is a week old or 10 years old, it can rule out or confirm what might be happening.
The tetras could be new fish and the corys be fish youve had for years, so that could lead to a conclusion that you bought fish that was carrying some kind of infection.
Yes, it might be internal parasites but you haven't provided much in the way of information to diagnose. Would you go to the doctor and ask him what's wrong with you without answering anything he asks? If we were there in your home we could do some water testing, but we aren't so you have to do it for us.
Anything you can think of will help. Was the food a newly opened package or have the fish been eating from that package for a while? Might you have done some cleaning in the room and sprayed some aerosols around? Might something have transferred into the aquarium off your hands?
hi! i’m sorry. i was panicking a little and didn’t get to that.
1~ Penguin tetras dying, they looked like they were almost having a stroke (twitching, stiff and swimming into things and dying shortly after. they look fine on the outside, but kind of curved like a rainbow after death?
2~ tank parameters (ammonia =0 , nitrites= 0 the water kit they sold doesn’t include nitrate tests so i’m going to look for it, but. temp 21°C, pH= exactly 7)?
3~ tank is 20 gallons, 3 feet long. 3x1x1 and has been set up for about 7 months now, and the penguin tetras and nerite snail were added last.
4~ Cherlam 6W hangon filter, with 2 types of sponge media. And a sobo sponge filter.
5~ 10 albino corydoras and 10 penguin tetras (now only 2 left) and a nerite snail. Tetras and snail were added last.
6~ i do about 20% water change weekly and vacuum over the sand/gravel bed, but vacuumed into the gravel a little about a week ago.
7~ tetras were added 3 weeks ago. along with a nerite snail. haven’t added anything new to the tank other than the fish.
9~ diet has been the same, the same half sinking pellets i use for both corys and tetras.
i asked the pet store and they said it looks like food poisoning. the food was the same food i’ve been feeding them, but i vacuumed the gravel in case there were any leftovers.
