What's eating my fishes?

[All the Fishes]

Ill try to keep this short.. Counting the fishes today in a 55, I noticed 1 of the 4 2" Bala Sharks missing. Upon finding the tail 1/3rd of it foating, I was going to net and remove the tail section, but it sank. My 2.5" Cuvier Bichir immediately snatched the tail and started violently shaking it as he was swimming across the tank! Ok... So.. I assume hes the culprit and remove him to place him in another tank and observe his behavior with the others. As I netted him, I notice his left front fin is ripped almost completely off!! Before I ask my QUESTION, Heres said tanks stock:
4.5inch silver arowana(very timid(had 2, but one died 2 weeks after my order came in..)
4 black khulii loaches(3.5-4")
2 synodontis catfish(1.5")
3 Bala shark (2")
3 tire track eel(6")
2 iridescent shark (2.5)
2 sailfin pleco (4")
1 black knife fish(3.5)
And the bichir.
Googling Cuvier Bichirs, I found someome who had added two 2" bichir to a tank with ten 2" mollies and a few guppies/tetras and he woke up to 1 molly left. (Pet store guy said they'd be fine together)
QUESTION: WHO DO YOU THINK ATE WHO IN MY TANK? Did the arowana attack both the bichir and the shark? Or just the bichir? OR did it lose a fin to the bala killing it and the aros innocent? The sharks have been bottom feeding and sifting sand for the passed few days so they were in the bichirs strike range frequently.. I'm not sure if it was the aro or the bichir or both i should be worried about at the moment. I havent fed any of my babies live food yet as to not make them bloodthirsty savages... A good 1oz Bloodworm feeding every other day and flakes/ cichlid sticks/shrimp pellets and dried shrimp daily 1 time is my regimen for this specific tank. Any input would be greatly appreciated.. At this point I'm assuming the aros innocent and have moved the bichir to a hospital tank treating the fin with melafix and salt. Thank you for anyone who took the time to read this

 

[KeepsWaterAndSomeFish]

I would like to start by saying almost all of your current stock isn't suitable long term. Most of it will seriously outgrow the tank, not to mention it will be insanely overstocked. As to which fish is the culprit it could one of many. At 2" silver sharks are relatively bitesize. It is possible that the shark died and was snacked upon. The damage to your polypterus could well have been from a confrontation with almost any of your species. Is this aquarium a growout or are you new to the hobby?

 

[All the Fishes]

I would like to start by saying almost all of your current stock isn't suitable long term. Most of it will seriously outgrow the tank, not to mention it will be insanely overstocked. As to which fish is the culprit it could one of many. At 2" silver sharks are relatively bitesize. It is possible that the shark died and was snacked upon. The damage to your polypterus could well have been from a confrontation with almost any of your species. Is this aquarium a growout or are you new to the hobby?

Went from 3 tanks to 21 in the last month. 4 55s 1 75 for when my cichlids eels and aros get bigger amd meed to be separated. Obsly need a 200+ gallon or 5 but I'm working on it... Ive got 2 tanks sitting empty at the moment. 4 more arent even filled with water nor do I have the stands built yet

 

[headbanger_jib]

The black ghost knife is reasonably bigger, and have the teeth to bite.

Bichir and eel as bottom dwellers will be harassed by synodontis, as synodontis usually suck slime off fish and this can cause infections.

 

[All the Fishes]

The fin that was bit at is like 90% gone.. makes me pretty sad.. He had some real character! The BGK apparently get ornery if not heavily fed is what I've been reading now... I'm super bummed I failed the bichir.. I'm gling to see how they do in pairs and probably get him a friend now

 

[tlindsey]

Tbh I would include the Aro, and possibly one of the Tire Track Eels as the culprit. How long has the 55 been setup? How often do you do water changes and what % is removed each time? What are your water parameters?

Welcome aboard

 

[headbanger_jib]

Bichirs love to be in groups, but you'll have to get rid of the synodontis cats, and your tank is a bit over crowded and will not sustain for a long period of time

 

[Backfromthedead]

imo the aro is the only possible culprit. seems unlikely that anything else could catch a bala in order to kill it. otherwise i also think it may have died and gotten munched on.

also, you better order several of those 200+ gallon tanks...

 

[MrsE88]

Just curious... since you have so many tanks at your disposal, why do you have all those guys together right now? I’d separate them. Not just to avoid situations like this, but to give them the very best living and growing conditions during this important developmental time. More fish in a tank means more fighting to get enough food. Not enough food will create more aggression and slower possibly even stunted growth.

 

[Davidiator]

My aro killed a 2-3" rose line shark and swallowed it without chewing it at all!
And he is 8-9" so they are not nice lol. I would say he It the culprit. Also as others said your tank currently is WAY overstocked and theses fish will slowly start to kill each other as they get bigger