Fish tank filter killing my fish?

How recently have you added the filter to the tank? For that matter, how long have you had the tank? If it is recent, then the filter is currently cycling, a process which can be dangerous to fish. http://www.fishlore.com/NitrogenCycle.htm. Neons are delicate and will not survive the cycle. However, it is absolutely vital. Without a cycled filter, you need to be doing 25% water changes a day, or your neons won't live long. If the neons are getting sucked into the filter intake, put some sponge into it or cover it with a net. That will stop them getting in.

Another problem is that you added all six at once. That would have caused an ammonia spike, quickly killing the delicate fish. Neons used to be hardy, but in recent years inbreeding has greatly reduced their hardiness.

The final issue is that the tank is too small. Neons are really active and need at least 15 gallons/60 litres or they will become stressed and die much sooner.

I'd suggest returning your neons to the store (say they were ill or something) and getting a fish that is more suited to your small tank, such as a betta. :)

Your filter only sucks in the dead. Fish die for many reasons like there own poo, soap resadu, maybe your tank ornaments where contaminated an you didnt rinse them right an your others happen to be more resistant than the ones that died. Your filter should be on at all times or your fish will start dying anyways. If your fish do bite the dust clean your tank carefully cycle your water for a month and try again. As for now try 25 to50 percent water changes w/ purified water make sure your water us at the right temperature for your fish sumwere around 73 fairenheit, and make sure you don't over feed them

The filter won't be killing your fish but will suck in a dead or dying fish.

Let me guess... the tank is new?

Unless you do a fishless cycle, which takes weeks, the fish poison themselves with their own wastes.

look here for an explanation of the nitrogen cycle - http://www.aquahobby.com/articles/e_ciclo.php

Do you know anyone with a healthy mature tank? The solution for you fish is to get some used filter media and swish it in your tank to seed your filter.

Otherwise start doing daily 40% water changes adding dechlorinator to the new water.

Have you tested the water or cleaned the filter? If you don't turn the filter back on the bacteria will die & the tank need to recycle.

Neon tetra are fast strong swimmers and couldn't possibly get sucket it your filter unless it is a super strong one. If your tank is new I guess it because you are feeding too much and they are dying of ammonia poisoning. You can easily see if they are being killed by the filter or not. Are they being sucket it alive and struggle to get out or did they die before that? I can understand if a betta or guppy get sucket it a filter and can't get out, but a neon tetra...All you should do now is remove the dead ones and do some large water changes.

LOL