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Katieryn 03-22-2012 09:50 AM

A weird Neon Tetra?
Hi guys!

This is quite an old problem but I'm quite interested to see if anyone has had anything similar or knows anything about this.

I've had this particular tank (10G) set up for ~5 months and had a group of 6 neons and 6 glowlights which have been in the tank for between 4 and a half months and 4 months (I added the groups separately) One of my neons is quite aggressive and I noticed he was attacking his fellow neons... wouldn't touch the glowlights.

I left him in the tank as I know that they are fin nippers and kept a close eye on him. Eventually I moved him into a tank by himself as one of scales has been dislodged near his mouth which has now healed nicely but it looks like hes got a beard :P When he was on his own he would turn around rapidly as if there was something going to bite his tail and he was going to fight back and then carry on swimming normally, I don't know if this could have been irritation from caudal fin healing. Hes still living on his own with 2 bristlenoses and looks quite happy swimming through the plants and rocks and is eating normally.

Hes been treated for any parasites and nothing has changed and the only symptom was the rapid turn which he still occasionally does. My tanks are water changed at least every week and tested regularly everything is at zero and there are traces of ammonia on some of the tests.

Has anyone got any ideas? Feel free to ask me a question if I've missed some info out ^^

Exterrestrial 03-22-2012 05:21 PM

Not sure why hes acting so weird. But he was being picked on because they didnt have enough space to set up territories. two schools are too much for a 10g. I would suggest just one school in there.

Katieryn 03-22-2012 07:51 PM

He wasn't being picked on, he was the bully. I watched very carefully to see who started the fight :P

Also he was doing this before I added the glowlights but I didn't think it was very serious...just a normal neon thing.

Any more ideas?

Byron 03-23-2012 12:09 PM

I can't offer suggestions on the behaviour because I simply don't know. But I am going to use this case to illustrate a point I frequently make, as it should help you and others avoid similar issues in the future.

All characins, most cyprinids, and some other fish are what we term shoaling or sometimes schooling fish. They must be in groups, and the number in the group impacts on their behaviour. Recent scientific studies, the first in this area, that I posted back when I came across it have proven that shoaling fish in groups under five will almost always show increased aggression. And fish species that would normally be deemed peaceful--such as neons, glowlights, etc--can suddenly become aggressive. The reason for this is clearly the lack of sufficient fish in the group. A very similar thing occurs in too small a space for the particular fish--and remember, too small here means to the fish, not to our perceptions of space being adequate for water quality and such.

The above issues stress the fish, to varying degrees. And just as with dogs, or even humans, each of us responds a bit differently to levels of stress, so too with fish. But whatever the level, it is a sign of frustration, and the fish is lashing out the only way it can. Sometimes it goes opposite, and instead of becoming aggressive it can become very withdrawn, even as far as to refuse to eat and simply waste away. In both cases it is a reaction to a situation that stresses the fish and it can't cope.

Back to the numbers; I mentioned five for the study, but there is ample evidence from the experiences of most of us that the more the better. The more fish in the group, the less the chance of stress related to the numbers, and the less chance of some reaction. The fish are programmed by evolution to live in groups of hundreds, and they have a number of needs within this group. There can be safety in numbers, social interaction, even normal aggressive behaviour (more obvious perhaps in fish like cichlids such as angels and discus). But this need is in the fish's genes.

I agree with Exterrestrial that a 10g is insufficient space for two species of shoaling fish. A 20g long would be much better, if that is possible. Or just one species, with 7 of whichever. These are the ideals. But another point has to be made, and that is that the effect of stress-related issues doesn't always show itself soon, but can linger and may or may not show up later. Stress weakens the immune system too, so that is another issue. And stressed fish always (as far as I know) have a shorter than normal lifespan due to the weakening effect of stress.

Hope this is of some help in understanding the cause.


Katieryn 03-23-2012 12:36 PM

I was thinking the same thing about not enough neons being in a group to be causing his aggression but I didn't want to put in any more neons due to the fact I had some glowlights. What confused me was when he was spinning around quickly when on his own, maybe this could have been a knock on effect from not having enough neons and still feeling quite aggressive?

The neons and the glowlights in the tank atm get on very well and shoal together none are aggressive or withdrawn and love weaving under plant leaves...guess i'm just lucky :P

Thanks for the info guys, I'll definitely be needing it in the future ^^

madyotto 03-24-2012 06:39 AM

i have 16 ish neon's in a 4FT tank and have one showing the exact behavioral problems

now he never actual bite's other fish
and he protects his little area near the filter and bushy plant

maybe he need some kind of territory just like mine yet alot of the time he schools up nicely and has no problems but prehaps for an hour or so a day he becomes aggressive chasing other neon's only from "his area"

but i second that that a 10 gallon tanks is very small for 2 schools and i am guessing from what you have said that there are not many plants and truly enclosed areas

now you say he swims through the rocks and plants like normal but is this in his new tank or the 10g one ?

Katieryn 03-24-2012 11:00 AM

These tanks are both 10G

The First tank he was in has a lot of plants and 2 small pieces of bog-wood and if he was shoaling he would nip the others but I also noticed he would sometimes go out of his way to nip a neon by itself when he was shoaling. He would mainly stay in open areas though, I don't know if he felt to scared to explore anywhere else in detail and find a nice hiding place for him to sleep.

The tank he is in now doesn't have as many plants and it's pretty new so the plants haven't grown that much yet and it has three small rocks in there, he mainly swims in the open area with the carpet plants and the rocks, rarely goes to the driftwood. Shall I try introducing the old neons into this tank? That would then split up the two schools and see how reacts to the situation?

Byron 03-24-2012 11:21 AM

Worth a try. I'd be interested in the results if you do this.

Katieryn 03-24-2012 11:44 AM

Okay I'll try it, wont be for a couple of days though as I'm a little busy. I'll let you know the results soon!

Katieryn 03-29-2012 05:09 AM

Okay since my last post I've sadly had to euthanise one of my neons which leaves me with 5 left. The four neons that were in my more planted tank (no behavioral differences due to number) have been transferred and have been in with 'beardface' for 24h now, he hasn't stopped the behavior and in that small amount of time there has already been a bit of damage to his caudal fin as there is one neon who sticks up for himself, the rest just hide.

I've made a video so you can see how he reacts, I'm sure you will know who beardface is :P What would you suggest?

DSCF0265.AVI - YouTube

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