I have a 29 g bio cube with many plants one Betta 2 albino glow-light tetras and a handful of cherry and crystal shrimp.Plus 1 galaxy (sole surviver) and one cardinal tetra (sole surviver).everything that is in this tank has been doing well.I started with a ph of 6.5 no amonia or nitrite-nitrates.The tank is 4 months old.
My problem is that i have attempted to add 3 sets of about 7 galaxies .The first time one lived so i asked the store what there water parameters were and then duplicated it on my tank thinking that maybe my water was not right for these fish.So then moved the ph up to 7 which is were there ph was at and tried again only to have the same result being all died with in 3 days.I basically did the same with cardinals in a different tank but read that Cardinal like a lower ph around 6.2 for instance tried 7 and one lived tried another 7 and they all died in 3 days.So basically i have one galaxy and one Cardinal alive and if i try to add more they die.Both tanks have fish that are doing excellent for 4 months now.I did find a cardinal head floating around is it a possibility that i have a nighttime psycho Betta that is killing these fish at night because i never see them floating or stressed at the bottom or top just gone all together and although i no the Betta cant eat them can it be possible that it is killing them and the tank is so planted i just cant see the bodies or is there something in my water that can be killing these fish? Thank you in advance.