I keep and spawn CPDs. I am a bit fond of them over chilis.... But buying in person is your safest bet, I have ordered and purchased in person and all but once ordering was perfectly healthy. The one not healthy group was gram negative bacteria, they looked fine acclimated fine and 5 of 13 were...
I breed and raise CPDs. My tap is 8.2
They do have a bit higher hatch and survival rate when I RODI and remineralize but beyond that I find no difference in life span, activity or health at my tap parameters.
Have you ever used any sort of parasite treatment in that tank or if you have live plants were they treated for parasites? Nerites are sensitive to most any parasitic treatments, even those which do not contain copper.
Not necessarily your issue but I had dragon rock and the same issue pulled the rock. Later went to try it again and found the culprit cleaning them after sitting. At least in my situation it worked.
I soaked them a while I don't know how long anymore but a few days at least and when I went to...
I'd move the existing fish. A move to a new 65g tank versus a stint in a 5 gallon bucket is considerably less stressful as they'll immediately be able to find somewhere to hide out rather than being cramped in a tiny space with all their friends and enemies with no where to go.
Its not permanent either. Hook it up run your zero water and let it drain store in a 5 gallon bucket in the closet. Cheaper on Amazon and other online retailers than direct which is what I've linked. I have the full RODI and you can add DI later to keep it a few bucks cheaper up front. Filters...
I don't either but the little RO buddy units are only like $45 and in short order it will be significantly cheaper than buying tons of cones and leaves and much faster than waiting for new water soak up the tannins enough to lower the ph.
Unless your fish are wild caught they will be fine at the measurements you have. Even wild caught should do well with proper acclimation your kh will be the biggest factor and for those fish you are well within their range.
Chemicals to control ph are almost always a bad idea especially when going lower from a high oh as it will yes lower your ph.... temporarily... and will bounce right back.
I ran myself a little test scenario on my tap in a 20 gallon tank a couple years ago.
API ph down I used 16 times the...
7.8 is not a bad ph. Mine is 8.2 and I moved here after having 7.2-7.6 for over 20 years.... Proper research and acclimation and most fish especially those commonly available will be fine.