My Neon Tetras Are Getting Eaten And I Have Nooo Idea Why

[Suzaku55]

Today I came home with 2 less neon tetras. All I found was a piece of flesh my the filter. I started with 5 now I only have 2. I have all friendly other fish in my 30 gallon tank. 3 cory catfishes, 1 adult female guppy and 5 baby guppies. One adult platy and then one baby platy both females. The platys are the newest to the tank so im suspicious, but aren't they friendly. My neon tetras are completely healthy they are colorful and schooling and eating. My tank is cycled and I do 10 percent water change every week twice a week so I know it cant be the water. I also feed them twice a day.  Someone help im lost I don't want my fish to keep ding

 

[the_lock_man]

A few questions and pointers for you.
 
Neon tetras are becoming more and more difficult to keep - have a read of this thread. I suspect that they may be dieing and then being eaten by the other fish - pretty much any fish will eat a dead one or a nearly-dead one. Certainly, none of the fish you list will usually attack a perfectly healthy neon.
 
How did you cycle the tank, and when?
 
I would increase your water change regime. 10% twice a week is the equivalent to 19% once a week - whereas most tanks need at least 30-40%. You may find that you have a build up of nitrate which the neons are susceptible to. What are your water parameters, by the way? Ammonia, nitrite and nitrogen readings, as well as pH, and if you know it KH as well.
 
I would also cut down your feeding, twice a day is too much. Fish have no mechanism to realise that they are full, which signals them to stop eating, so they are on the seafood diet (as in, I see food, so I eat it ). It could be that overfeeding is adding to your issues. You should feed the fish a varied diet, primarily flakes, but regular veggies (I feed mine peas, carrots, swede, and the very occasional piece of cucumber), and a treat of live food no more than weekly. Many people deliberately fast their fish for a day. I will go further and fast mine for 2 or 3 days in a row - they are quite capable of surviving for a week and more without food.
 
Just one other point, I would suggest getting 3 more of the same species of cory, as they are a shoaling fish, in the wild they live in groups of hundreds or thousands, generally 6 is the point at which they lose count and assume they are in a large group. Same with the neons, although I would definitely be inclined to let the last two neons die, and replace them with cardinals which are hardier and brighter coloured.