Sorry to hear about your losses donnaR. From what you described, it sounds like the tetra may have had finrot as well. In regard to the ich...don't take it so hard. It's the most frequent plague of
FW and nearly everyone has had to do battle with it.
The biggest problem with ich is it's already done damage to your fish before you even notice it. By the time the cysts are formed and visible, your fish are already severly weakened. This may have been one of the reasons for the fin nipping. A weak fish will more than likely be preyed upon by other fish...further weakening the fish to the point of no return.
There are several ways to deter ich infestations in the future:
1. Never buy fish from
LFS that have just arrived. There is a greater chance of dormant or live ich being present at this stage. This is the source of almost all ich infestations. Sometimes this is not an option (distance to
LFS...availability of fish, etc.
2.
QT - This is suggested in lieu of or in concert with the above. Sometimes this is not a viable option. Keeping new fish in
QT for a few weeks will allow you to watch for any signs prior to adding to your tank. In retrospect, you will be doing the job of the
LFS in your home.
3. Tank temp - Keeping tank temp at 80 - 82d consistently (if your fish can tolerate it) Most fish can. Ich cannot strive in higher temps.
A number of fish are known to be ich carriers for some unknown reason. Clown loaches and bala sharks are two that come to mind immediately. Do some research and beware of
LFS tanks that have these in combination with other fish.