Welcome to the forum Red97!!!!
I agree with ...KEP..., it would be good to know a little bit more information so that we can help you out better and more accurately. If you could, click
HERE to open a page which will help you understand what types of information would be helpful and then try to answer the questions that are listed as best as you can.
I am willing to bet that ...KEP... is thinking the same thing as I am right now - your tank is not cycled right now (click
HERE to learn more about cycling if you are not already familiar), or you simply have too many fish in this tank. Granted, neon tetras are small fish, and they do enjoy schooling with others of the same species, however, 30 of them is a bit over kill IMHO and IME. Both of these factors would certainly be stressful on your fish and may be the source of your troubles right now.
Additionally, can you tell us how you added (acclimated) your new tetras to this tank? (i.e. floated the bag to match water temps and then let them go) While I have never had this problem myself, I have heard/read about quite a few hobbyists finding out that neon and cardinal tetras are a bit more 'fragile' than is often spoken about so it may not be all that abnormal for you to lose a couple fish shortly after bringing them home. IMHO, the best bet is to use the principles and techniques which are layed out in the article you can find by clicking
HERE to acclimate your fish in a way which will help to reduce the occurrence of death. And yes, I realize that the article may be oriented a little bit more to wards saltwater fish/inverts, however, I feel as though they are still valid and very useful when applied to freshwater livestock as well.
Lastly, are you 100% sure that what you bought home really are neon tetras and not cardinal tetras or the type of neon tetra that you can see by clicking
HERE? While you picking up something other than neon tetras may be unlikely, I am sure it has happened in the past since some LFS may not be all that vigilant about their accurately labeling the fish they sell. On the other hand, if all 30 fish are neon tetras, I wonder if the color fading is simply due to the stress involved with being bought and brought to your house and, in time, would brighten up again. In fact, I believe that neon tetras would really prefer to have a lot of hiding places in which they can quickly dart to regardless of where they are in the tank; so perhaps your four plants are just not enough to provide that security to all 30 of your neons
