Tri-colour shark sudden aggression 11/12/09
Hello,
<Hello,>
I can across your site this evening while researching tri-colour or Bala shark aggression. Unfortunately I did not find anything that might help to explain the situation in my tank of late.
<Well let's see what we can do...>
We have a 50 gallon tank with 1 iridescent shark, 1 tri-colour shark, 2 yellow gouramis, 2 blue gouramis, 1 angelfish, 2 Chinese algae eaters, 1 Pleco and a red-tailed shark.
<Your tank is WAY overstocked! The two Gyrinocheilus ("Chinese Algae Eaters" despite not coming from China and not eating much algae). Pangasius catfish are simply massive fish, and schooling animals too. They get to some 120 cm long in the wild, and even in aquaria are upwards of 70 cm on a regular basis. As for Bala Shark (Balantiocheilos) these are also schooling fish, and the Plec (likely Pterygoplichthys pardalis or similar) these get to about 45 cm and need tanks bigger than you have even by themselves, let along with all these tankmates. There is no way this system is going to work long term.>
Both of the larger sharks, the iridescent and the tri-colour have been together in the same tank for 3 years now over the last few days the tri-colour has started nipping and biting the iridescent shark. He does not appear to be bothering any other fish except the biggest fish in the tank.
<One issue is he's frustrated. These are schooling fish, and kept alone are likely to become neurotic. Schooling fish aren't "peaceful" in a mindless sort of way, they're actually highly social with a strong pecking order instinct. When we ignore this, they sometimes become aggressive as this built-in behaviour tries to express itself. Do read here about this species:
http://www.wetwebmedia.com/FWSubWebindex/bala_sharks.htm
>
There have been no changes in the tank in quite some time. Any idea what could/would cause such a sudden change in behaviour?
<While I can't suggest the exact trigger, the bottom line is you made some bad choices here and are keeping these fish in the wrong numbers and in the wrong aquarium. Had you not done this, you wouldn't be having these problems.>
Thanks!
<Hope this helps. Cheers, Neale.>

Re: tri-colour shark sudden aggression  11/13/09
This is what I figured. We inherited the tank and most of the fish were already with it so we did not think it was a problem.
<Ah, I see.>
It looks like I'll now have to do some separating.
<Guess so.>
Thanks for your advice.
<Happy to help. Good luck! Cheers, Neale.>

Survival chances. Ariids and Balas? 06/15/07 Hello! <Hail and well met.> I'm writing in regards to my 2 Colombian Sharks (about 2 inches long, maybe less). Well, the two that are left. (One died this morning.) I've done a lot of research lately and feel that these little guys are doomed. <I hope not! Among my very favourite fishes. A bit worried about doing research on fish *after* buying them, but I'll let that pass for now.> Currently, they live in a 55 gallon tank with 2 Bala shark. <Wronger than a wrong thing on the wrongest day of the year. Bala sharks are freshwater fish, Colombian sharks brackish water fish. These two species cannot be kept together for any length of time.> We're using the filter pump that came with aquarium. (It's a PetSmart aquarium kit). I don't think the filter is enough. <Possible. A ball-park figure for fishes this size would be 5-6 times the volume of the tank in turnover per hour. Perhaps a bit more if you can, because Colombian Sharks especially love strong water current. In static water they tend to end up treading water close to the filter pump.> We plan to add a under gravel filter. <UG filters can be an excellent choice in brackish water tanks. Set one up as per a marine aquarium, with a filter plate, crushed coral, gravel tidy, and then coral sand on top. Use two powerheads, one at each end of the tank. This'll generate lots of water movement as well as keeping the pH high and the hardness level appropriate to the fish. On the downside, the Bala sharks will hate such water conditions, but they're going to hate the salt even more...> After reading your FAQs, I learned that they are saltwater fish. <Not really saltwater fish. Hexanematichthys seemanni is a true estuary dweller, and adults as well as juveniles swim up and down estuaries far into freshwater but rarely any distance out to see. So while they do very well in saltwater tanks, they certainly don't need saltwater conditions. 50% seawater, or SG 1.010 is fine. High pH and hardness, and especially lots of water current, seem to be more critical.> I thought they were just brackish water fish. <They are.> I'm glad to know this because my husband disliked the idea of doing just a brackish water tank for these guys. Although, he really likes these fish. <As does everyone who keeps them. They look like sharks, but don't get too big (30 cm is typical), and are as gentle as kittens (except to anything they can eat, of course).> Here's my issue. I believe that I can not get anything bigger then a 55 gallon tank for them any time soon. <That's fine for now. Growth is fairly rapid for the first year, when they'll get to about 20 cm, but after that, growth slows down quite a bit. But long term, yes, you may have a problem. Realistically though, rehoming these fish shouldn't be hard. Big adults are always in demand for additions to jumbo brackish tanks or fish-only marine aquaria.> I live in a trailer home. I just don't think the floor with support a 100 gallon tank. It might support another 55 gallon tank at the other end. It may be half a year before I can afford another 55 gallon tank. Do these guys stand a chance of surviving that long with two Balas in a freshwater tank? <Difficult to say. Their tolerance of freshwater is very high, and specimens 10 cm plus can survive in it quite well, assuming the pH and hardness are high. I've even seen fully grown adults in freshwater tanks. They weren't happy, but they were alive. I wouldn't recommend keeping them in freshwater though. For one thing, you'll find they become increasingly neurotic, seemingly looking for a way out so they can swim "downstream" to the estuary.> If I do manage to get them into another 55 gallon tank and make it brackish water, how long do you think I can keep them in such living conditions? <Forever. They do fine in seawater, but do just as well in very hard, pH 8.0 brackish water at SG 1.010.> I plan to purchase a real house (eventually) and do a saltwater tank. This may take a few years and I have no idea if these guys will survive until then. If they do, will they get along with blue tangs and clown fish? (These are the kind of saltwater fish I /think/ I want) <I've kept Colombian Sharks in saltwater tanks with things like Panther groupers and Domino damselfish without problems. Anything too big to be swallowed whole will be ignored by them. Pufferfish work very well. The only problems I had were with Triggerfish, which hated the clicking sound these catfish make (the trigger attacked the cats, the cats clicked in distress, and trigger attacked even more aggressively).> What size tank would you recommend for a beginner in saltwater tanks? I know the bigger the better. I suspect that even 100 gallon tank might not be larger enough to start out with. I might as well find out now and start saving my pennies. <Indeed, the bigger the better. I guess it depends what you want to do. For fish-only aquaria, a 55-100 gallon tank is a great idea because you can keep a nice selection of the large but colourful animals that wouldn't work in a reef tank, like Triggers, Puffers, Lionfish, Morays, etc. Definitely worth sitting down with a good book and having a read. Bob Fenner's "Conscientious Aquarist" is excellent, and I say that without him looking over my shoulder telling me too!><<Hey! I see this here/now! RMF>> Thanks in advance for you advice. <No probs.> P.S. I would consider talking my husband into returning these fish to Petsmart, but they have new rules. They have decided that you should not have more then one shark in a tank. If you do, they will not accept returns. <Ah, a beautiful example of a Stupid Rule. For one thing, they're treating all fish with the word "shark" in its common name as being somehow similar. The problem with common names, and why experienced aquarists tend to dump them in favour of Latin names. What they mean to say is that people should only have one Labeo spp. or Epalzeorhynchus spp. "shark" (such as Rainbow and Red-tail Sharks) to each tank. That is indeed correct. But the Colombian Shark is not at all closely related to those fishes, and absolutely must be kept in a group. The bigger the group in fact, the better.> We were told by a fish store that Bala Shark, Colombian Sharks and Rainbow sharks would do well together. <Rainbow sharks definitely are aggressive and territorial. Bala Sharks and Rainbow sharks both need freshwater, Colombian Sharks brackish, so not really a viable combo.> Now, my rainbow shark lives in a 10 gallon by himself for sending a Bala Shark into shock. (Which ended in death.) <Oh dear.> The Bala and Colombian sharks get along fairly well and even try to school with each other. <How sweet! Both species need pals. Colombian sharks are rather adorable in this regard, and adults and juveniles school quite happily. People are sometimes worried about adding new catfish to the group, but no, they seem to really enjoy the company.> I suspect the employees are the fish store are pretty knowledgeable, they just refuse to tell us the whole truth unless we ask the right questions. <Perhaps. I can see where the Pet store is coming from, but in this case they've extended a serviceable idea way beyond its boundaries. Cheers, Neale.>

Bala Sharks and Goldfish 10/16/06 <<Hi, Missy. Tom>> I have a tricolor shark.  And I used to have a goldfish in with it. <<Not the best idea to mix tropical fish with Goldfish, Missy.>> Well today when I walked past the tank I heard a loud sound like one of the fish jumped.  When I looked over the goldfish was dead and part of his skin was off.   Do you think my tricolor shark did it? <<Tri-colored (Bala) sharks are almost legendary for their non-aggressive behavior toward other species although, if kept in an aquarium that's too small - anything under 75-gallons is probably too small - their behavior might become questionable. These fish are "high-strung", for lack of a better way to put it. They actually do better in groups which really starts to force the required size of an aquarium upward, probably larger than most hobbyists would have room for or care to maintain. So, to answer your question, I'd say that it's possible that your shark was responsible for your Goldfish's demise.>> I noticed a few times that the tricolor shark and goldfish were chasing each other.  I was just wondering because my son wants another goldfish and I don't know if I should. <<I wouldn't put another Goldfish in with the shark, Missy. Once again, if your aquarium isn't large, your shark may very likely injure itself by smashing into the sides and anything else in the tank. And for what it's worth, no Goldfish should be kept in a tank smaller than 20 gallons and, preferably, 30 gallons or bigger.>> Thank you Missy <<You're welcome and good luck. Tom>>

Bala Sharks <Craig...would you please help this gentleman out? Thanks. David Dowless> <Absolutely!> 90 gallon tank: I want to get a group of Bala Sharks and some compatible fish to make a community. I know Balas get quite large eventually. How many should I add right away? How big a group is logical to add in the near future? --Thanks, Charlie <Hi Charlie, These fish can reach 14" in length and can be "aggressive".  Compared to the other minnow sharks they are relatively peaceful, but still will chase/nip on occasion so stick with fish of a similar temperament that can stand up under the pressure or that live out of the water column and are also tougher fish. The group of Balas will make any other choices more important. In a 90 you could probably accommodate 3-5 Balas (they are shoaling type fish) and perhaps a Pleco (watch size here, some can become quite large) perhaps a few Clown Loaches. Some of the larger Barbs would likely do alright as well, they are feisty and fast.  It is best to avoid overcrowding (start slow) and introduce the aggressive fish last, concurrently if small, and change decorations/set-up to throw territories off during intros.  Make sure your tank is well covered, Balas are notorious jumpers.  Best of luck, Craig>     

Was Goldfish disease enquiry, now tropical/Betta health, comp.    4/12/06 Hi, <Hello> I'm Karthik. I'd contacted you about that skin flukes/Trichodina problem that my goldfish were suffering from for quite a few months. I lost one Oranda due to dropsy. I treated all the rest with a dose of Potassium Permanganate and then dismantled the entire aquarium, cleaned everything thoroughly and then re-established the aquarium and allowed the empty, re-setup aquarium to stand for a fortnight to allow the beneficial bacterial colonies to develop. I then added my fish back into the tank and now they seem to have got rid of their problem and their behaviour patterns are all normal now. I thank you sincerely for all the assistance you had given me during that time. I'll feel free to contact you in case I need your assistance at any point of time. <Okay> I wanted to know one more thing- I have another aquarium (tropical fish). I have a school of neon tetras, 4 Bala sharks and a rainbow shark. <The Neons will be consumed here> I also have 5 bettas- a  red crowntail, a blue halfmoon tail, a royal blue veiltail, a dark red scissor tail and a Cambodian female betta which I house in separate (obviously), spacious jars. They're all doing extremely well. However, when I add any of these 5 bettas to my tropical tank, they sort of become dull and their fins start tearing in various places after 2-3 days. There are lots of hiding places, and plants like the Cabomba, Amazon sword, etc. and the current due to the filter isn't very strong either. If I put them back into their jars, they become normal again and their fins grow back. I've checked the tank- there are no pH, ammonia, nitrite and nitrate level surges. the temperature is maintained at 24C The water quality is quite good because the other inmates of the tank are doing pretty well and I can assure you that none of these other inmates harm the betta. <Perhaps not overtly> I'm puzzled about this sudden change of behaviour from these bettas. Could you tell me what could be the reason for this? Expecting your reply soon, Thanking you, Karthik <Likely "stress" from being in the presence of the sharks, particularly the Redfin... plus having so much space to swim about in... is wearing on little-used fins. Bob Fenner> Re: Goldfish disease enquiry ... minnow shark, betta comp.    4/12/06 > Hi, <Karthik> Thanks for the information. Now I would like to clarify a few things here. Firstly, both the Bala sharks and the rainbow shark are about 1 to 1 and a half inches long. They're still very young. Are you sure the presence of the rainbow shark affects the behaviour of the betta? <Absolutely. More so though, as you hint, with increasing size> As far as I can see, the rainbow is pretty peaceful and he's happy grazing the leaves of the various plants in the tank and nibbling at everything he can find including the gravel and in fact, that's all he seems to be doing all day. <You will see, learn in time... please see WWM re "Minnow Sharks"... beh., comp... I am in the process of sorting, writing review pieces for principal species...> The bettas and the rainbow shark are supposed to be compatible species anyway. <Not often, no> And how come these bettas don't feel uncomfortable if I leave them alone in a large tank with just the rainbow shark? I've tried that before). <Not long term> You'd mentioned that the neons would become a meal of these sharks in your previous reply to me. I've been careful to choose balas of the appropriate size considering the fact that Neons are existing in my aquarium. They're doing well. I know that neons are from the Amazon and balas are from Thailand but would you recommend this combination? <No... the Balas get too big (35 cm.) are too rambunctious, like very different water quality...> After all, neons reach a maximum size of 2-3 inches <... rarely more than half this> but Balas grow up to 12-13 inches or so I've heard. I've also heard that the rainbow shark gets extremely aggressive as it grows older. Is this true? <Often, yes> I've never had a rainbow shark before. I've had almost all varieties of goldfish over a decade (ever since I was 8, now I'm 19) but I'm trying to expand my knowledge in other tropical fish now- hence the above questions. Expecting your reply soon, Thanking you, Karthik