I'm looking for a small (nano) sized centerpiece fish for my 20 Long. It has aquasoil and CO2 in it, so the pH will sometimes go to or lower than 6.0. One website said that they recommend keeping them at pH 6.5-8.0. Now, with other fish that are said to be kept in >6.5 pH, such as otos and honeycomb catfish, are doing fine in the tank right now. But the more basic leaning seems to say that they might not do well in my water. What do you think? And if you wouldn't recommend Dario dario, what would you for my tank?