I've been thinking about this subject about fish dying in our tanks days after we bot them. It seems that many of us seem to pinpoint the cause at water parameters (which probably is). But I think that there are other factors which may be the cause too.
One reason could be that the fish that we bot are already in a bad shape. Fishes caught in the wild are sometimes done with chemicals to stun them before collecting. Add in the stress of packing and shipping them to our LFS, by the time they arrived, they are already in bad shape. Also I have seen the way some lfs house their livestock, simply pathetic.
Being able to choose a healthy fish would greatly reduce the risk of it dying in your tank. When I started my hobby, I cycled my tank for about 2 mths till the parameters are right, slowly add in live stock, do regular housekeeping but still have fish dying on me. Couldn't figure out why till i started getting my livestock from a better known lfs. And all the deaths stopped.
The important factors to a healthy tank in my opinion would be-
- water parameters (PH, salinity, bio filtration, etc)
- buy healthy fishes
- Get the right compatibilty of fishes
- regular checking of parameters
- good diet
- proper knowledge
Just my 2c worth.
Cheers