Hi, I m planning to set up a tank with tetras. I know that tetras prefer a pH of 5.5 to 7, and this should be fine since presently the pH in my tank is low. To set up a tank for tetras I need alot of plants. My questions is that if I add alot of plants, will they lower drastically my pH level? At the moment I only have Water wisteria plants and 3 small pieces of lava rock and the the pH falls from 7 to 6 in 10 days or less!
Also, what's the ideal number of tetras for a 120 ltr tank? I have 2 algea eaters, 2 bronze catfish, 8 adult mollies and 10 molly fry (2months). I m planning to remove the mollies once I ll buy the tetras.