@imw I really am sorry about the confusion you are experiencing. And I am familiar with your other thread on the fish deaths (which I sorted out therein as to the actual cause).
Unfortunately, pet store employees are not trained (for the vast majority of stores, there are some hobbyist-run stores but they are rare) in fish physiology, habitats, and requirements. Many of us will say the same--do not rely on their advice, ever. If I had listened and accepted much of the "advice" I have received from store staff in years past, I would not be in this hobby now, solely out of frustration with the lack of success that would have followed this inaccurate advice. Research and only research should be your guide, and that includes a forum like TFF.
The Penguin Tetra, which is probably the species
Thayeria boehlkei as this is the most commonly seen of the three species in this genus in the hobby, occurs (its natural habitat) in the Rio Araguaia in Brazil and the Peruvian Amazon. The waters in most of the Peruvian Amazon area are acidic (pH well below 7 for most, certainly not above) and very soft (zero GH). The parameters for the Rio Araguia are pH 5.8-7.5 (6.5), 4-20 dH (8), 72-82?F (22-28?C). Early dry season pH would be 7.0 (6.7-7.3), the late dry season 6.9 (6.6-7.0)
. Unlike the other two species (
T. obliqua and
T. ifati) in the genus, this species can be maintained in slightly basic (alkaline) water aquaria but it is not necessary. The fourth species, T.
tapajonica, was only described in 2017 and is very unlikely to be common in the hobby.
Soft and somewhat acidic water is ideal. This will not cause "fish deaths" unless the fish are species requiring harder water (with a basic pH to match), such as livebearers.
