My killifish pair, and a male peacock gudgeon trying to duke it out... what to do?

I’ve had a female gardneri killifish alone in a 20gallon for a couple weeks now. I keep the male in a separate tank because his pursuit of her is relentless and stressing, and the last time I left her alone with him for a while she ended up with many torn fins. A few times I added the male to her tank so they could breed and had no issues with their behaviour, apart from her swimming away from the male a lot.

For this tank I had always planned to get at least one peacock gudgeon, and as I learned more about them, decided to get a trio with two females and one male. They were in quarantine for a few weeks and one of the females died, as well as her replacement. The other female has been doing fine and successfully laid eggs which have now hatched into healthy fry.

Since the fry were hatched and fish done with quarantine, I decided it best to finally add them to the 20 gallon. I added the female last night and noticed the female killi following her a lot. I assumed it was curiosity. I woke up this morning to find that the female gudgeon’s fins were torn and I’m frustrated that the female killi had decided to be nasty and hurt the other fish.

I thought it would be best to add the other fish now to minimize targetting of the lone female and perhaps the male would defend her.

I then saw I would have to add the male killi too, as the fry in the spare tank were small enough to have slipped through the divider into the section I keep him in, and I saw several in there. They would be far too small to catch, much less find and round up so I decided to try putting the male in the 20 gallon, and I was hoping he would “bully” the female enough to stop her attacking the female gudgeon.

Well, instead what happened was the male gudgeon immediately started trying to duke it out with the female killi; circling her, flaring his fins and puffing out his gills, and she did the same. The male gudgeon seemed to intimidate her enough to where she ignored him but swam away when he got too close. But the male gudgeon also kept doing this to the male killi while I was acclimating him in a clear container in the tank. The male killi is the largest of my fish at ~3.5inches and the biggest a**hole because he's chased and nipped the fins nonstop of every. single. fish. I’ve tried to keep him with. I had hoped the distraction of other, larger fish (than before) would keep him occupied, but no.

The female killi, for some strange reason, also did not welcome the male at all. When I put him in the tank, she was acting very aggressive and territorial. And the male gudgeon decided to join in.

I feel bad for the female gudgeon as the male killi chased her whenever he saw her. I dont know what’s with killifish and female gudgeons but the chasing got bad enough that the male started fleeing too while the female killi, exhausted or overwhelmed, sat on the ground and was just breathing there. Since the male killi was being too big of an antagonizing jerk as he always is, I quickly put him in the breeder box in the tank to not attack more fish.

Now I know some aggressive fish need time to establish a hierarchy in the tank. I assume that is what these guys are trying to do, along with territory? I didn’t expect the gudgeon to put up such a front but I’m glad he’s standing up for himself. Should I let them sort it out (apart from the male killi because clearly he’s too big and nasty to be trusted with other fish) or should I separate them for a while, if not for good? Should I separate them so they don’t get too stressed too (even in a net or something)?

I really had hoped they’d get along... hoping still that at the very least I can get the female killi to coexist with the gudgeons peacefully, as she’s smaller and younger than the male.


Here is a video of the “fight ring” behaviour I saw.

 

The Peacock Gudgeons and the male Killi have virtually identical shape and colors. They think they are in a territorial dispute with one of their own kind! The female killi mistook the Gudgeons as male Killies, and because they were smaller than her, she was aggressive toward them. What you have are some very confused and aggravated fish.

 

That's nothin...I just brought home an orphaned bully jack Dempsey chiclid and threw him in my 55 gallon with my common rainbow shark who is also a bully and I've been watching these two for the last 45 minutes just roostering in the tank chasing each other, they just now finally gave up, the chiclod is a touch bigger but the rainbow is a touch meaner and way faster....let it work itself out.

 

I had hoped their confusion would fade but the male gudgeon still swims over to the female killi every once in a while to flare at her (she’s in a net to stop chasing the poor female gudgeon)... yeeap fish are not the brightest lol

So female killis are aggressive to males smaller than them or something? That’s interesting, but unfortunate since they don’t seem like they’re going to realize they’re not the same species any time soon... I had the same issue with my first gudgeon, the male killi got frustrated chasing her constantly trying to breed with the poor thing...

 

I had hoped their confusion would fade but the male gudgeon still swims over to the female killi every once in a while to flare at her (she’s in a net to stop chasing the poor female gudgeon)... yeeap fish are not the brightest lol

So female killis are aggressive to males smaller than them or something? That’s interesting, but unfortunate since they don’t seem like they’re going to realize they’re not the same species any time soon... I had the same issue with my first gudgeon, the male killi got frustrated chasing her constantly trying to breed with the poor thing...

What if you added one obnoxiously bigger fish in?
In my earlier ignorance at fish keeping I ended up with 3 rainbow sharks...it did not work for a long time, I had my bigger male common in my 28 gallon,and the 2 albino females,whom are much smaller..in the 55.
The albinos are friendly but as they get bigger they will seperate, I finally realized they need distraction and alot of hiding, I put all my 16 tetras in the 55 and the common rainbow and he chased for a day or two but it stopped and last night i finally saw them do it they were schooling all together in my wave maker current. Fish all have personality,we just need to guess how to make them happy haha.
Get 1 bigger fish and like 10 neon tetras and distract the kuhlis and gundgeons....spread the aggression out.

 

What if you added one obnoxiously bigger fish in?
In my earlier ignorance at fish keeping I ended up with 3 rainbow sharks...it did not work for a long time, I had my bigger male common in my 28 gallon,and the 2 albino females,whom are much smaller..in the 55.
The albinos are friendly but as they get bigger they will seperate, I finally realized they need distraction and alot of hiding, I put all my 16 tetras in the 55 and the common rainbow and he chased for a day or two but it stopped and last night i finally saw them do it they were schooling all together in my wave maker current. Fish all have personality,we just need to guess how to make them happy haha.
Get 1 bigger fish and like 10 neon tetras and distract the kuhlis and gundgeons....spread the aggression out.

That’s a good idea but I’m worried more problems might arise as a result... the killies are cowards, chasing the smallest fish as soon as they’re not looking (both kept chasing the female gudgeon when the male stopped for a sec)... hm but a bully to bully the bullies would have to be one that would ignore smaller fish... I don’t know what could fit the bill without being a bit too dangerous/aggressive. Killies are semi-aggressive and apparently gudgeons are peaceful (though this male is fighting against that label lol), so it’d have to be pretty calm but able to hold its own and put them in their place. Fish never seem to behave as you’d want or expect in a group, that’s for sure.

 

That’s a good idea but I’m worried more problems might arise as a result... the killies are cowards, chasing the smallest fish as soon as they’re not looking (both kept chasing the female gudgeon when the male stopped for a sec)... hm but a bully to bully the bullies would have to be one that would ignore smaller fish... I don’t know what could fit the bill without being a bit too dangerous/aggressive. Killies are semi-aggressive and apparently gudgeons are peaceful (though this male is fighting against that label lol), so it’d have to be pretty calm but able to hold its own and put them in their place. Fish never seem to behave as you’d want or expect in a group, that’s for sure.

Your fish are dull in color...I'd try a brighter fish peaceful but larger than the four...I know you said they chase small guy but I'm still saying 4 or 6 neon tetras..get the blue and red stripe ones... maybe they will be so distracted by the bigger fish they wont bother to chase the smaller guys.

 

Not likely to change, as the two species will always have a similar color pattern, so will see the other as conspecifics. And since both species are territorial, the disputes will not end until fish die.

 

Just curious, did you end up needing to separate the gudgeons from the killies, Shelilla? Hopefully no deaths?

I'm unfortunately not too surprised about the issues, since I know most killies can be somewhat aggressive. Gudgeons will also sometimes have issues with similarly patterned fishes as chromedome52 mentioned, despite being otherwise peaceful with most species.

 

Just curious, did you end up needing to separate the gudgeons from the killies, Shelilla? Hopefully no deaths?

I'm unfortunately not too surprised about the issues, since I know most killies can be somewhat aggressive. Gudgeons will also sometimes have issues with similarly patterned fishes as chromedome52 mentioned, despite being otherwise peaceful with most species.

I did, the female gudgeon had a bunch of splits and tears in her fins and I knew from past similar experiences with killies that this just wasn’t gonna work out sadly. The male lives in a separate tank alone now. The female randomly died one day while they were together- I have no clue why but I suspected stress ): in any case, the gudgeon pair is doing very well. Just 2 days ago they had a batch of eggs finally hatch and now there is at least a hundred tiny fry in the tank. They are good parents, the mom has ignored the fry and made no moves to try to eat them surprisingly. The dad worries me a bit because as soon as the fry hatched not even a day later the female laid more eggs and he never comes out for food while he’s fanning them and was more interested in the female than eating when the fry hatched. But at least there’s lots of babies! I also have 3 now-juveniles from their first batch which I plan to put in the tank when the fry have grown a bit. I bought killifish eggs online as I was having no luck with mine and so far I have at least two hatched fry who have survived for 24 hours. Not great odds, but at least they hatched at all. The ones from my original pair would get fungus on them no matter what and just end up dying. I suspect they were too far related or something along those lines. I’m going to grow the killi fry up alongside some gudgeon fry and I’ll be curious to see if they can adjust to get along with each other.

 

They are good parents, the mom has ignored the fry and made no moves to try to eat them surprisingly. The dad worries me a bit because as soon as the fry hatched not even a day later the female laid more eggs and he never comes out for food while he’s fanning them and was more interested in the female than eating when the fry hatched. But at least there’s lots of babies! I also have 3 now-juveniles from their first batch which I plan to put in the tank when the fry have grown a bit.

Congrats on the fry! My male has been the same way with regards to coming out for food, and ended up dropping some weight because of it. I've since been spot feeding him frozen foods with a pipette right next to the nest, which thankfully has been helping.

So lucky that your parents aren't eating the fry! I was hoping for the same, but thus far they've eaten them every time if I don't catch them soon enough (hence I only have a handful of fry). In my case, it's always the female who's interested in hunting them down.

 

It is very unusual for the Gudgeons to not eat their fry, this is the first time I've heard of it. Perhaps it's how the tank is decorated, but congratulations on having such a pair.