Molly bothering Koi

Nov 4, 2008
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#1
Do Koi and Mollie's not "get along"?

My housemate has a small 10 gallon freshwater tank, and we recently added two guppies, a sucker fish, and a koi to a tank containing a molly and rainbow shark(?). Yes, I know you shouldn't put a koi in such a small tank (plus there are temperature conflicts), but I had no say in that one. My housemate couldn't be convinced otherwise.

As soon as he put the koi in the tank, the white molly immediately started sucking/nibbling the backside of the koi. This has persisted for the last couple hours. Is this normal behavior? Do we need to separate them in order for both to survive?

Thanks for the help!
 

dogdoc

Large Fish
Sep 6, 2005
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#2
Without even knowing what the "sucker fish" is (I'm presuming a pleco), you are way overstocked.

I would say that probably the only fish that should remain in that 10 would be the guppies and possibly the molly.

How long has this tank been set up? Is it cycled?
 

FishGeek

Elite Fish
May 13, 2005
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South Carolina
#3
ummm....Koi will get 3 feet in length! You might want to make them aware of that. And you and your house mate really need to do some research on keeping fish. Your tank is horribly stocked and is only going to cause more problems. I highly recommend reading the stickies in this forum.
 

Nov 4, 2008
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#4
Without even knowing what the "sucker fish" is (I'm presuming a pleco), you are way overstocked.

I would say that probably the only fish that should remain in that 10 would be the guppies and possibly the molly.

How long has this tank been set up? Is it cycled?
Ha ha... sorry I know I'm probably a nuisance in this community, but you have to start somewhere, right? Pleco sounds right...

Trust me, if this was my personal tank, I'd definitely be doing things differently. This tank was paid for and is maintained by my housemate. The tank has been set up for about... 2 months or so. Yes, the tank has more or less been cycled (we've had fish in it from that first month). I don't know what kind of maintenance/upkeep my housemate has done.

So any idea what's up with the koi and molly duo?
 

Nov 4, 2008
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#5
ummm....Koi will get 3 feet in length! You might want to make them aware of that. And you and your house mate really need to do some research on keeping fish. Your tank is horribly stocked and is only going to cause more problems. I highly recommend reading the stickies in this forum.
Yeah... I (and he) know. He's a little stubborn and said he didn't care. Like I said, I don't exactly have control over this tank.

I will take a look at those stickies though. Again, sorry if I/we disgust those of you in this fish community...
 

dogdoc

Large Fish
Sep 6, 2005
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#6
Mollies IME can be a little pesky to other fish. But I think you are missing the point here.

The Koi can get huge, and is really a cool water fish. Not compatible with the other inhabitants at all. The pleco if it is a common, again can get to well over a foot in length. The rainbow shark, about 6 inches. None of these fish should be in a 10g by themselves let alone together.

Do you know what the water parameters are in the tank (ammonia, nitrite, nitrate, pH)?
 

dogdoc

Large Fish
Sep 6, 2005
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#7
No, I think you misunderstand. We are all trying to help. But, If "he doesn't care" and you can't get him to care, then we are all wasting our time and effort trying to help.

Nobody is disgusted by a lack of knowledge. We were all there at some point. It is the lack of caring that will make people on the forum angry.

But, I can tell you one thing for certain. Unless you change the stocking in that tank ASAP, all of those fish will be dead very soon.

Doc out.
 

Nov 4, 2008
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#8
Mollies IME can be a little pesky to other fish. But I think you are missing the point here.

The Koi can get huge, and is really a cool water fish. Not compatible with the other inhabitants at all. The pleco if it is a common, again can get to well over a foot in length. The rainbow shark, about 6 inches. None of these fish should be in a 10g by themselves let alone together.

Do you know what the water parameters are in the tank (ammonia, nitrite, nitrate, pH)?
I'm not missing the point. I know our tank (and its inhabitant mix) are terrible. I just wanted to know what was going on with the koi and molly.

I'll have a little talk with my house-mate and share these aquarium "basics." Maybe we can get this tank turned around :)
 

brian1973

Superstar Fish
Jan 20, 2008
2,001
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Corpus Christi, Texas
#10
Im not going to beat you up..welcome to the tank..

Obviously you care or you wouldnt be here..I dont think anyone is going to give you the exact answer your looking for due to the facts doc stated above..he knows what he is talking about..and to second what he said..really doesnt matter what your roommates think those fish if left in that tank will be dead within 6 months or so in my opinion. The worst thing we see here is newbies coming here and not taking the advice..asking for help is not a nuiscance (sp?) but as doc pointed out it is a waste of time if you dont take the advice given..I seem to have plenty of time so it doesnt matter to me..lol. Many or most of us came here for the same reason..overstocking, sick, etc..we listened we learned and some of us stick around to pass that info on to newbies..some learn and move on. some dont listen think we are picking on them and leave, believe me we arent picking on you we are trying to save you and your fish suffering down the road, some people post here saying how they love their fish so that wont change the setup or get rid of the fish, but in truth they are killing their beloved pets.
Hopefully your roomates will listen and make some changes, Aquariums are very addicting and enjoyable but you have to meet certain conditions or they are a PITA and your fish will die.

Again welcome to the tank hopefully you will stick around and learn as much as you can and find out how enjoyable this hobby can be.
 

Nov 4, 2008
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#11
Im not going to beat you up..welcome to the tank..

Obviously you care or you wouldnt be here..I dont think anyone is going to give you the exact answer your looking for due to the facts doc stated above..he knows what he is talking about..and to second what he said..really doesnt matter what your roommates think those fish if left in that tank will be dead within 6 months or so in my opinion...

...Again welcome to the tank hopefully you will stick around and learn as much as you can and find out how enjoyable this hobby can be.
I appreciate that. I am hoping to learn a bit about all this aquarium stuff. It's quite a bit more involved than you'd initially think...

Ha ha, my situation's a little more complicated. The thing is that I have to convince my roomie to get rid of things that HE bought. I'm the one who purchased the molly and 2 guppies... which seem to be the right kind of fish for this size of a tank. The pleco, koi, and rainbow shark are all his... and a good deal more expensive than mine. Gotta love it...

I'll pass along this info and see what he says.
 

brian1973

Superstar Fish
Jan 20, 2008
2,001
3
38
Corpus Christi, Texas
#12
I appreciate that. I am hoping to learn a bit about all this aquarium stuff. It's quite a bit more involved than you'd initially think...

Ha ha, my situation's a little more complicated. The thing is that I have to convince my roomie to get rid of things that HE bought. I'm the one who purchased the molly and 2 guppies... which seem to be the right kind of fish for this size of a tank. The pleco, koi, and rainbow shark are all his... and a good deal more expensive than mine. Gotta love it...

I'll pass along this info and see what he says.
Suprisingly guppies may not be the right fish for this size tank either..lol..it depends on the sex of each..females are typically prego when purchased..they are live bearers..think of guppies/molies/platies as the rabbits of the fish world..if you have a m/f you may, probably will, quickly become overstocked just from babies..lol...but yes size wise they are correct for this size tank..just have all males or all females.

Let him read what we have said...He will have only wasted money when they die.
 

Nov 4, 2008
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#13
Suprisingly guppies may not be the right fish for this size tank either..lol..it depends on the sex of each..females are typically prego when purchased..they are live bearers..think of guppies/molies/platies as the rabbits of the fish world..if you have a m/f you may, probably will, quickly become overstocked just from babies..lol...but yes size wise they are correct for this size tank..just have all males or all females.

Let him read what we have said...He will have only wasted money when they die.
Ah man! :eek: Alright... yeah give me some time to hopefully get this mess under control
 

jo3olous

Large Fish
Aug 6, 2008
909
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Philadelphia, PA
#14
I don't think any of the fish will exactly die right away but;

If typical fish behavior occurs:
-The redtail shark is very territorial and should be bouting the pleco for hiding places and surface area eventually
-The Koi will outgrow the tank or die of stress
-The pleco if common will outgrow the tank, and is such a big bioload (poo/pee) that constant water changes and paremeter readings will be necessary
-The livebearers (guppies) will produce tons, but it's not like the fry will survive with all those other fish in the tank! (food!)
-The Molly must hate that koi (lol)

How big is the koi anyway, if it's still a juve it might live in that tank longer than we think. The main issue is that everyone is pretty much right about stocking issues (both bioload and tankspace for each fish)and you might not see the effects of it right away, but rest assure they will all die from stress, not old age. ~ Just my 2 cents on what can/will probably happen to the fish
 

Nov 4, 2008
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#15
I don't think any of the fish will exactly die right away but;

If typical fish behavior occurs:
-The redtail shark is very territorial and should be bouting the pleco for hiding places and surface area eventually
-The Koi will outgrow the tank or die of stress
-The pleco if common will outgrow the tank, and is such a big bioload (poo/pee) that constant water changes and paremeter readings will be necessary
-The livebearers (guppies) will produce tons, but it's not like the fry will survive with all those other fish in the tank! (food!)
-The Molly must hate that koi (lol)

How big is the koi anyway, if it's still a juve it might live in that tank longer than we think. The main issue is that everyone is pretty much right about stocking issues (both bioload and tankspace for each fish)and you might not see the effects of it right away, but rest assure they will all die from stress, not old age. ~ Just my 2 cents on what can/will probably happen to the fish
All that you say makes sense. The koi is relatively small right now. I know they get huge, but how fast are we talking?
 

bunker_1

Large Fish
Mar 24, 2008
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Cincinnati
#16
I know someone that had one grow 6 inches in a couple of months. I do not know if that is typical or not. I would think that when it is time for him to start growing, he will dominate the food supply.
 

FroggyFox

Forum Manager
Moderator
May 16, 2003
8,589
10
38
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Colorado
#17
they grow pretty quickly...but all fish are healthier and grow faster when they are in ideal situations. In other words, if your fish are competing for food and space right now they will be less healthy and grow more slowly than if you had them in a much larger tank. Of course, like someone pointed out, the Koi would do much better in completely different water conditions as they are a coldwater fish.

Mollies and gupplies also do better when there are more than one...either a bunch of females, a bunch of males or at least two or three females per male.

Perhaps you could have your housemate come here and read this thread? It really would be best for the fish if you re-homed most of them and really decided what would be best in the tank.