roadmaster
Fishaholic
I have went through your posts (approx 40), and you have clearly had more than your share of problems.
You began by saying the tank was 20 Litres and then mention was made of 16 Litres?
You have posted nitrAtes as high as 50 ppm approx a month ago, and now you report zero. Have you, as asked already,done a tank swap? Either of these two mentioned tanks would be too small a volume of water to be able to maintain water quality for more than a single Betta and perhaps some shrimp. (in my view)
Is possible that the surface area available for bacteria to colonize is I suspect,, small. And as such, too many fish will create more waste than the filter can process, = sick fishes.
Is also possible as mentioned earlier, that you have purchased sick fish or fishes ,or possibly fishes best suited for soft acidic water with pH between 6.2 and 6.8 rather than the 7.5 to 8.0 moderately hard water that you have reported in earlier posts.
Is true that some fish can adapt to perhaps slightly less than ideal waters with respect to pH and or GH, Kh , and temp, but some don't.
Much to be gained by acclimating fish slowly.
I believe tetras will always do better in more acidic water as opposed to alkaline conditions, and many tetras will fair much better in cooler waters. 74 to 76 degrees F would suit most.
As I see it , you are attempting to keep too many fish in too small a tank.
Larger tanks are way easier to maintain with fewer problems, and you could always use you present tank for quarantine tank to help prevent possible disease from being introduced to otherwise healthy tank by quarantining all new fishes before they are added to the larger,(cycled) tank.
