# Fish Compatibility



## Lolliejj (Mar 3, 2013)

Being a newbie to fish keeping, I didn't check out fish compatibility when I bought my fish. I asked in store and was told all my proposed fish would get along fine. I was upset to find , when I later searched online, that most of them are not supposed to get on well together.

So far in my tank, which I have had for about a year now, I have 4 Harlequin Rasbora, 1 Flying Fox and a Molly. I used to have 2 Mollies, but one died of Dropsy. I added 3 Kuhli Loaches and a Rainbow Shark about 2 months ago.

Looking at the compatibility charts and such, I have been informed that the Harlequins, the Molly and the Loaches should not get on with the Flying Fox and Rainbow Shark, but I have found that the Molly and Rainbow Shark have become very friendly with each other, the Harlequins don't care for the Rainbow Shark or the Kuhli Loaches, but are happy with the Flying Fox and Molly, the Loaches are happy with every other fish and the only 2 that seem to ever have a little spat now and again are the Rainbow Shark and Flying Fox which are the 2 that are supposed to get on.

Can anybody tell me why it appears any information that I have been told does not seem to apply to the actual fish in my aquarium? I am very confused at the moment. Will there be a massive fight where everybody in my tank falls out at some point and follows the information about compatibility?

Much thanks for any ideas or questions answered! :-?


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## jaysee (Dec 9, 2009)

Welcome to the forum

This happens all the time. It only makes sense that the person working in the fish department would know, but more often than not they don't have a clue. Unfortunately that's just something people have to learn on their own.

As for the fish - compatibility can be a tricky thing. Fish are not robots, and while they may supposed to be a certain way, and may usually be that way, there are always exceptions. As someone new to the hobby, it's common to misinterpret behaviors. I'm not saying that you are, but often what one person sees as playing is actually the beginning stages of a confrontation. It's rare that fish just "throw down" - there's usually a process that escalates to a full on fight. The warning signs are there before that happens, but one needs experience in order to identify them. Too, a fishs behavior can change dramatically once they are mature - the dynamics of the tank can change. As fish grow, there becomes less space in the tank and territorial fish, like the shark, begin to expand their territories. BUT, the fish don't have to actually fight for there to be problems. Stress is a killer, and will take its toll in time.

Without knowing the size tank you have, I cannot speak to the suitability of the fish.


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## Lolliejj (Mar 3, 2013)

Thank you very much, I have a 29g tank, but if any problems persist, my next door neigbour has a 75g tank and is a very avid fish keeper (only just found this out!) So he would be willing to take fish off my hands if they fight or misbehave.

I think my tank may be a little over crowded, and reading information online again differs from what I was told when I bought the fish. It seems I may have to give some to my next door neighbour anyway.


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## jaysee (Dec 9, 2009)

I'm not familiar with the flying fox, but it would be best to give the shark to your neighbor, if they'll take it. The rasboras and kuhlis will do well in the tank. The mollies will too, though some people feel that they require a more brackish environment. I'm not big into live bearers so someone else will probably provide you with better info on them.


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## Lolliejj (Mar 3, 2013)

I will check to see if he has a shark already, as if he does it could cause more problems to him and then I would feel bad. Alternativley, I may buy another tank, large enough to keep the shark in and then make sure it is kept with compatible fish. Thank you for all your information. I have had my Flying Fox for a year now and it seems to be very docile. It has never ever 'gone' for any other fish it had been kept with before. It got very big very quickly so I had to buy a bigger tank for it. I can do the same again for the shark instead.


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## jentralala (Oct 5, 2012)

The rasbora and Kuhli will do great together, I own both of those fish in my 35 gallon tank. I would suggest increasing both of their numbers, they both like the company of others of their species. Once you are able to remove the shark you may want to look into increasing their school to 10, and the Kuhli around that number as well. 

Now...this gets to the tricky part. What is the GH, KH, and PH of your tap water? You have combined hard and soft water species, and your water may not be suitable for some of them.


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## Lolliejj (Mar 3, 2013)

My pH is 7.1, my gH is about 6 and my kH is also about 6. Is this bad or good for my fish? :/


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## Byron (Mar 7, 2009)

Commenting solely on the fish mentioned, I would remove both the Rainbow Shark and the Flying Fox. Both will outgrow your 29g tank, both can get aggressive particularly with each other but often other fish too. BTW, the names shaded so you can click them for our fish profile, have a read there, it will explain this more.

Rasbora are shoaling fish, meaning they live in large groups, so you need a few more. They are peaceful, one of the most peaceful fish. A group of 8-12 would be fine in your 29g. Check the profile; your probably have the Harlequin Rasbora [click the shaded name...], but there are two similar species, the Lambchop Rasbora and Hengels Rasbora. All are fine, they are in the profiles with photos.

Molly are livebearers and thus need harder water than the other fish, and this is especially important with the common molly. When we know the GH and pH, we will know better on this fish.

Byron.


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## Lolliejj (Mar 3, 2013)

I did once have 6 harlequins but unfourtunatly the molly that got dropsy ate one and attacked the other, leaving it a weaker swimmier, meaning it got trapped in my filter. I am reluctant to get rid of the flying fox as I have had it for a year, it has not changed size so far and has not attacked any other fish. It has now taken to hiding from the shark, even though it is the bigger fish. This is also confusing me, as surely it could just 'put the other fish in it's place'?


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## Byron (Mar 7, 2009)

Lolliejj said:


> I did once have 6 harlequins but unfourtunatly the molly that got dropsy ate one and attacked the other, leaving it a weaker swimmier, meaning it got trapped in my filter. I am reluctant to get rid of the flying fox as I have had it for a year, it has not changed size so far and has not attacked any other fish. It has now taken to hiding from the shark, even though it is the bigger fish. This is also confusing me, as surely it could just 'put the other fish in it's place'?


What you are observing is most likely fear on the part of the Flying Fox. As I think someone mentioned earlier in this thread, we cannot guarantee the behaviour of every individual fish, but we can assume they will behave according to the species norm. The Rainbow shark is likely beginning to exert its dominance, and the Fox is likely beginning to be stressed by this. When it comes to two aggressive or semi-aggressive or "domionant" species, one is going to lose--or be killed trying to fight back.


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## Lolliejj (Mar 3, 2013)

I am going to take the Shark back to where I originally bought it, even though I do not expect money back, I do not want to inflict it on my neighbour. Hopefully they will take it back.


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