First of all I want to thank you guys for helping me identify my eel. I haven't felt this kind of help in a small community anywhere else.
Now for the tetra's we had a dissappearing issue when we had a rainbow shark. We ended up getting rid of the shark and getting tetras till we had 20. Now we're down to 12. I currently have 3 swordtails, 2 loaches, a small brisslemouth pleco and a larger pleco that survived. Plus 2 eels, one that was answered here and another is a zigzag eel.
Am I having a problem with hiding spots? I know I don't have enough plants. I'm thinking of getting more moss and covering the area under the wood structure on the right.
Or are they getting sucked up the filter? I thought this but couldn't find any evidence in the filter system. Any advice would be fully appreciated.
Here's the pleco I'm questioning. 
You're not rude. I have seen the mouth but mostly made the question because of how big the mouth is.
Thank you for taking it well. As a follow up I asked my mom who has had plecostomuses since before I was born. She said they will only eat them if they are already dead. So it is possible but something else is killing them
Yeah it was ultimately the bichir. I posted a few pictures in this post. Had to get rid of it. Luckily my fish guy took it off my hands and replaced a few of the tetras for it even though I didn't get the bichir from him. He was very upset at whoever sold me the bichir and said they'd be ok with the tetras. The more you know.