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50 Gallon tank.

My school of rummynoses has been under attack the last 2 nights. One dead and one injured is the result.

The other inhabitants of this tank are:

6 Zebra danios
4 Tetra pristellas
2 Female Platys and one male
1 Farlowella
1 Ottocinclus
1 Emperor Tetra
1 Bala Shark, relatively large
4 small Amano shrimp
5 relatively small Yoyo loaches

The lady at the fish store thinks the yoyo loaches may be to blame. The zebras though feisty tend to mess with themselves only. The Bala shark has the size to kill em but has never had a past of attacking anyone and seems very peaceful towards everyone. Those three are the main suspects.

She was telling me that Yoyo loaches tend to be very active at night time and may be the ones attacking the rummys...

What do you think of that scenario or who would you blame on these sudden attacks?

ETT

Loaches can hurt other fish, but the major thing is the fin nipping. If yoyos go predator you will find most of your fish get fin nipped in a very small space of time. They can be indescriminate and share those bites around.That a rummy was killed outright and only one other injured makes me think it was the bala. For a bala a dead tetra takes only one bite, and their supposedly peaceful nature cant be taken for granted. Some specimens will become increasingly aggressive to the point of of fully territorial when they mature. Its not usual, but its common enough to be undeniable. Bala sharks can get to nearly a foot in length. Its too big for that community or at least it has the potential to be, and sometimes the brain races ahead of the body! The size difference between other fish and itself may eventually become too tempting an advantage for it not to exploit.You might just be witnessing the tip of the iceberg.

Sometimes just certain combinations in community make fish edgy. It might be the yoyos bombing about that is freaking the bala, or the presence of the bala that makes the yoyos nervous.Thats when things get bitten. Sometimes a fish may bite another that wasnt involved in an incident because its frustrated. I have silver dollars that pick a fight with each other if one of the acaras intimidates or takes a shot at one of them, but theyre too ckicken to take on the acaras. Similarly a bala might get frustrated if a yoyo takes a shot at it, especially in the dark when things get confused, it lashes out at the closest fish, and that might be the tetra instead of the yoyo that started it all.

I think this one is too close to call, youll have to put a blue led in there or something and watch them to be sure.Loaches can be great peaceful scavengers or a complete fin removing machine of manic attackers, it depends, and a bala can be a gentle giant or a territorial hell. Basically you have two major candidates for violence in that tank, and they might be making each other worse. Neither species would be my first choice for a community that includes small fish like rummynoses.

That stock seems very ad hoc. Was it planned or did you just buy whatever you liked and add piecemeal?

The profile for the Bala Shark here on fishprofiles.com says: "Usually peaceful and passive but will violently attack invertabrates, such as ghost shrimp and snails as they make up a major part of its diet in the wild. The greater number of sharks in the school the bolder they will be; single specimens are extremely timid."

The 1 tetra on it's own... will it be happy? They are schooling fish that feel more secure in groups.

I recommend deciding how you would like to stock the tank and plan it well. Separate the others out into dedicated setups if you are set on keeping those species. Or return to the shop for credit.

If you want to do the new setup around the bala because he is your pride and joy then go for it... but not sure the community is going to work as it is currently .... I would strip back and start again with planning.

btw salespeople.....their job is 'selling'... famous last words "they shoud be okay"..... I always conversationally ask shop staff what setups they have (or if they have the type of fish they are netting for me)

... most aquarists love to 'talk tanks'. If they don't have fish themselves then...... be dubious about their advice.

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~~~ My fish blow kisses at me all day long ~~~

wish ga, who would you blame for the recent attacks?

Yoyos are active(mine were mostly active during the day) but I never saw any of mine go after a fish. Occasionally bump a fish but never do any damage and usually they were good about completely avoiding the other fish when they went bouncing around all over the place. Other than that they seemed to ignore every other species in the tank. I would not suspect the yoyos unless their activity level is stressing the rummies out even though the loaches aren't touching them. My first guess would be the bala. If it's relatively large it may have gotten to the point it's trying to eat smaller tankmates. Only other thought is the other schooling fish or platy are getting nippy. I've had issues with danios before and won't stock them except with other hyperactive fish.

I would also suspect the Bala, or a combination of the Yoyos stressing the Bala out. I have Yoyo loaches in my 55g planted and they are very active, especially at night. I have 7 Rummynose tetras and none have ever been injured or killed. My Yoyos have a piece of driftwood that is like their playground, so they pretty much keep to themselves during the day (can't say that at night ).

I'd defintely check the tank at night with a LED light or something so you can see if anything is going on.

*Kristin*

Its probubly the Bala Shark, as they can be aggressive when stressed. As far as your stocking goes, I am concerned about your Otto and your Emperer. The Tetra is a schooling fish and would be much happier with 5 other tetras to play with and the otto, while not a schooling fish, tends to be more comfortable when other ottos are in the tank with it.

Another possible suspect that wasn't mentioned is your danios. While they are typically a peaceful fish (especially when in schools) they have a tendency to nip at colorful fish and are very active (especially at night) Watch your danios closely to see if they exibit some of these behaviors.

Another aspect is that your tank is a bit crowded. Sometimes peaceful fish, when put under stress can become more nippy or aggressive. Also, your perimiters may go up and that too, could be bad. I would do a water test to see where everything is at chemically, because the chemical balances in the water may also bring out the aggressiveness in some fish, because they are uncomfortable. With aquariums, it is better to look at every possibility and not to underestimate any fish, because sometimes the culprit could be the one you least suspect (for example, I had an apple snail, a small one by the way, that attacked and consumed five guppies in a single night!)

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Also, how many rummy noses do you have in that tank as well You mentioned a school, so I assume you have (or had) at least six....

That in mind, this is what I would do:
6x rummynoses?
6x Zebra danios
3x Platties (I actually would consider taking these out- they have a tendency to multiply, or sticking with one sex)
4 Tetra Pristellas (actually consider upping thier number too)
1x Farlowella (Whiptail Catfish right?) or 3-5x Ottos
6x Emperer Tetras
1x Bala Shark
0x Amano Shrimp (The Bala Shark may eventually eat those. The shrimp would look nice in a planted one-gallon tank though)
5x Yoyo loaches (which actually may eventually overcrowd the bottom of your tank, they get to about 5" each, while they are schooling you could lower thier number to three and they would be fine)

I think your tetras would be fine in larger numbers, as long as you have a decent filter. The only thing I would watch out for would be the bottom as it looks a bit overcrowded. I would also try and limit your schools(6 or more fishes) of tetras/danios from 4 to 3.

Hope this has been a help to you ^_^ Good luck with your future aquarium keeping

Inky