Who is biter in my tank? Please, help!

[newhobbist]

I have 72g community tank with all fish listed in my signature. Here is damage done to my fish within last 2 days:
Elephant Nose - one very deep bite and one a bit smaller one on its side (most likely, I will loose it)
Pictus Cat - one very deep bite right behind gills (it does not look good also)
Pearl Gourami - smaller bite on the side (will, most likely, heal)
Goby - bite on his tale (looks like it's been done by a pretty large mouth)

I have no idea what happened and who could do this. My fish coexisted peacefully for a long time. My latest additions:
2 Australian Rainbows (2 months ago) - even though they grow fast, I've never heard that this can bite others.
2 Paradise Fish (2 weeks ago - could be biters, but they are much too small for such huge wounds.

In my opinion:
Silver Dollar - might be the one
Barbs - usually fin biters
Rainbow Shark - the most agressive fish in my tank, but has quite small mouth IMO.
Bolivian Ram - the oldest in my tank and lived other fish without bigger fight in past.
Am I overlooking something???
There were no decoration rearrangement, dramatic water quality change, or any other activity that would trigger this behavior.

A'm going for vacation tomorrow and will be back in 11 days. Hate to think that this problem might continue, or, even, grow worse.

 

[Menagerie]

72g bowfront with Emperor 400:
Gouramis: 1 Opaline, 1 Gold, 1 Pearl
Bolivian Ram, Purple Spotted Gudgeon, Pictus Cat
2 Weather Loaches, 2 Australian Rainbows, Elephant Nose
Gold Nugget Pleco, Rainbow Shark, Silver Dollar, 2 Paradise Fish, 2 Rosy (or Cherry) Bards
6 Long-Finned Zebra Danios, 3 Cardinal Tetras
Plants: Banana plant

I'm not too sure, but it could have been done by a group of fish--you wouldn't necessarily see the individual bite marks. I also think one fish can make multiple bites and you might think it was only one bite. I'm leaning towards the shark or the barbs; I don't know about silver dollars.

 

[newhobbist]

I'm not too sure, but it could have been done by a group of fish--you wouldn't necessarily see the individual bite marks. I also think one fish can make multiple bites and you might think it was only one bite.

It is just easier to assume that one fish got suddenly crazy then think that there is "mad fish" desease.
I'm also pretty sure that those weren't multible bites. Elephant Nose got his first wound very deep with skin hanging off. Bites are not large, but very deep (flesh is exposed on Elephant Nose as well as on Pictus).

 

[lovemybarbs]

My bet is that it is the shark. Has he been chasing any of them?

I got rid of my red-tailed shark because he starting attacking all of my fish when I upgraded to the 55. When I introduced the new fish, that was the last straw. He put bites into every fish I added to the tank as soon as they hit the water.

 

[zephyr]

i'm goign to say, in order of what i think,
shark, pearl or opaline gourami, barbs

sharks are notriously aggressive

the medium sized gourami's can be really aggressive at times too, which shocked me recently cause i have always ignored that because ones i used to have where so calm
but the pearl's i have now have been attacking the three flamboyant guppies i've had, leaving only one alive with me tyring to heal its fin!

and well, i've alwyas hated barbs, thast it really, lol,nah but they can be nasty little pieces of work


CHECK WHICH FISH SEEM TO BE CHASING OTHER FISH, OR ACTING TERRITORIAL, LOL

 

[newhobbist]

The Shark is the most agressive one, but it never actually harmed other fish. And, even though it has chased my Pictus quite often, it never bothered Elephant Nose.
Pearl Gourami was bitten also.

Also, it is agression, not predatory behavior because all small fish are alive and ok.