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FAQs on the Redtail Black Minnow Shark

Related Articles: Redtail Sharks, Freshwater Minnow Sharks, Bala or Tri-Colored Sharks, Redfin Sharks, Black Sharks,

Related FAQs: Minnow Sharks 1, Minnow Sharks 2, FW Shark Identification, FW Shark Behavior, FW Shark Compatibility, FW Shark Selection, FW Shark Systems, FW Shark Feeding, FW Shark Disease, FW Shark Reproduction, Bala or Tri-Colored Sharks, Redfin Sharks, Black Sharks,

For Dr. Monks         9/14/16
Just wanted to send you a quick thank you for some wonderful laughs this morning! I love www.wetwebmedia.com <http://www.wetwebmedia.com> and it is my go to site for when I need help answering a customer's question. I looked up info regarding treating red tail black sharks for ich, and nearly fell out of my chair, your sarcastic wit was so on target! We all wish we could give similar responses to our customers here on a daily basis!
Thanks again for being you! Keep on fishin'!
<Well, thanks for the kind words! Much appreciated. Humour is difficult to get right 100% of the time, especially when you're talking with people from all around the world. And yes, sometimes we do get kinda cranky, but that's really more about being animal lovers and consequently frustrated by problems with animal welfare. But I do think we help more people than we annoy, and have helped them to look after their pets so much better than otherwise. That's what makes this fun to do! On the other hand, I have had a few "can I speak to the manager" moments here at WWM, and God bless Bob, he's usually in my corner! Again, thanks for the kind words, and good luck with your Red Tail Shark.
Cheers, Neale.>
Re: For Dr. Monks       9/15/16

LOL, you actually turned your red tail shark person around and they ended up apologizing and thanking you!
<Oh! Have to go back and look at that thread!>
Unfortunately, if I ever told a customer exactly what I thought they should hear, I would not have a job by end of the day!
<Understood. As a teacher, I'm often in situations where I have to hold back (by adult standards) and listen to teenagers, try to remain sympathetic, and do my best not to take their insults personally. So yes, I agree, oftentimes honesty *is not* the best policy!>
Occasionally, I do manage to reach someone, by going about it in a roundabout way, but it's not easy. I loved the points you made when you referred to cats and dogs. It constantly amazes me how little people care about their fish and turtles, and how they rarely do any research prior to getting a new pet, especially turtles. I have a rescued one in a 90 gallon tank with lots of swimming room, weekly water changes, and a big canister filter. She's so spoiled she has toys! She loves her water ball and her rubber ducky, I kid you not.
<I believe you! There's increasing evidence that reptiles are smarter than we gave them credit for, and that being the case, adding stimulation to their lives through toys and scenery is probably worthwhile.>
Your customer was particularly dense, yet you managed to make her understand, in the end. Kudos to you and Dr. Fenner both! Keep up the great work, I'll continue to recommend you guys as always!
<Much appreciated, Barbara. Take it easy, Neale.>

red tail shark       6/28/15
I have a red tail shark. I have no troubles but I am curious. My tank just finished cycling and I had a small oil slick problem at the top of the tank. To my amazement the shark seems to have eaten it. I knew they ate algae. Also he still goes to the top and swims upside down. He seems to inhale air then as he comes down he releases bubbles. I was wondering if
this species can breath air? I can find no mention of it online. Thank you for your time.
<Short answer is no, they aren't air breathers, though many fish will inhale the uppermost layer of water if oxygen levels below the surface aren't great. Couple this with the oily slick, and these two bits of data suggest a combination of overfeeding and under-filtering. Specifically, turbulence at the surface will break down the oily film, dispersing it throughout the water column so the biological filter can break it down.
Review water turnover rates. A Red-Tail Shark needs a minimum of, say, 55 US gallons. So with a recommended turnover rate of 6-8 times per hour, that's 330-440 gallons/hour. Check your filter provides that, and if not, add a second filter. Cheers, Neale.>

red tailed shark acting neurotic; just acting like a RTS      9/10/13
Greeting.  I have a 29 gallon tank with 6 neons, 2 swordtails, 2 angels, and 2 red tailed shark.
<Aye yi yi..
. troubles ahead. The angels and minnow sharks will eat the neons; and two of the RTs won't live in this volume.>
 All are new. 
 <Is this system cycled?>

All are small. I ordered 1 red tailed shark but there were 2 in the bag when I got them via 2 day delivery.  The red tailed shark in question was the bolder of the 2.  It only hid on day one.  It had an orangish tail on day one - I couldn't call it bright red.  On day 2 it took up residence in the upper back corner of the tank where the heater is and started to appear to "look up" or "look at itself" in the reflection on the back wall of the tank.
<This is the subdominant individual. It should be moved NOW. If you don't have a breeding trap/net or divider, a floating plastic colander will do>
 Although I have fake plants and ornaments and driftwood for it to hide, it has been staying in this corner of the tank in the open.  On day 3 the other shark, which had been hiding all this time seemed to join it and even seemed to mimic it but didn't stay only in the corner like the neurotic one.  On day 3 also shark #1's tail was extremely pail, even white.  I read that was a bad sign.  Shark #2 still has an orange tail.
 I had tetra flakes that I was feeding and saw everyone eating except the red tails.  I got on the internet and researched what they eat and got some frozen shrimp brine today, day 4.  Neither seemed really interested but shark #1 did not budge from his corner while shark #2 went missing for a while and certainly could have been eating.  Every now and then shark #1
will become somewhat limp, float head up and seem listless and then regain control.  These episodes last probably less than a minute.  He (or she) just seems obsessed with staying in that corner and "looking at itself." 
I see no evidence of conflict between the 2 sharks and there is peace in the overall tank.
 <What you are describing is "non-physical" combat>
I turned the light off early tonight, if only to prevent it from continuing to look at itself so it would have to find something else to do.  Any ideas what might be happening?  Is it doomed?  Thank you very much.  Deb.
<Do search/read on WWM re the species. Bob Fenner>
red tailed shark acting neurotic    Neale's (as usual, better) go     9/12/13
Greeting.  I have a 29 gallon tank with 6 neons, 2 swordtails, 2 angels, and 2 red tailed shark.
<Ah, now here's one problem! Red-Tail Black Sharks don't cohabit; at least, not in aquaria. Unless you have some insanely large aquarium (200+ gallons) they just won't tolerate one another. Remove one as quickly as possible.
Long term, even one specimen is too much for 29-gallons except within the shortest possible time-frame (a few weeks). You'll need 55+ gallons for a singleton bigger than, say, 5 cm/2 inches. They're big fish when mature, and grow quickly when well kept, and they're also very active and
All are new.  All are small. I ordered 1 red tailed shark but there were 2 in the bag when I got them via 2 day delivery.  The red tailed shark in question was the bolder of the 2.
<Bolder = bully in this situation.>

It only hid on day one.  It had an orangish tail on day one - I couldn't call it bright red.
<Is some variation, depending on mood, genes, gender and age. Often the truly deep red colour comes with age and under subdued lighting and good conditions; stressed fish tend to "fade".>
On day 2 it took up residence in the upper back corner of the tank where the heater is and started to appear to "look up" or "look at itself" in the reflection on the back wall of the tank.
<Again, a clear sign of territoriality.>
Although I have fake plants and ornaments and driftwood for it to hide, it has been staying in this corner of the tank in the open.  On day 3 the other shark, which had been hiding all this time seemed to join it and even seemed to mimic it but didn't stay only in the corner like the neurotic one.  On day 3 also shark #1's tail was extremely pail, even white.  I read that was a bad sign.  Shark #2 still has an orange tail.
<See above.>
I had tetra flakes that I was feeding and saw everyone eating except the red tails.  I got on the internet and researched what they eat and got some frozen shrimp brine today, day 4.
<Not really their prime diet. In the wild they feed on "aufwuchs", the mix of algae and tiny invertebrates that encrust rocks and leaves. A mix of fresh green algae, soft or blanched vegetables (such as lettuce and courgette); algae wafers; and small invertebrates like bloodworms and brine shrimp fit the bill nicely. Variety is key, but with the understanding they're omnivores not carnivores, so balance green and meaty foods wisely.
Bright light to spur green algae growth is a major plus.>
Neither seemed really interested but shark #1 did not budge from his corner while shark #2 went missing for a while and certainly could have been eating.  Every now and then shark #1 will become somewhat limp, float head up and seem listless and then regain control.  These episodes last probably less than a minute.  He (or she) just seems obsessed with staying in that corner and "looking at itself."  I see no evidence of conflict between the 2 sharks and there is peace in the overall tank.
<May well be no fighting yet, but will be... give it time.>
I turned the light off early tonight, if only to prevent it from continuing to look at itself so it would have to find something else to do.  Any ideas what might be happening?  Is it doomed?
<In the wrong tank, yes, the species becomes stressed, throws itself about, and often jumps out to an early death. Basically, they're the wrong fish for your set-up.>
Thank you very much.  Deb.
<Red Tail Black Sharks are one to a tank, and one to a BIG tank at that.
Hope this helps. Cheers, Neale.>

Stocking With A Redtailed Shark    6/13/12
Hi Guys
I have a stocking question. I've recently lost (in the last year) most of my tetra fish (black skirts and phantoms) due to various occurrences and old age (no tank problems besides an ill-advised incident with a molly
<Mollienesia live in very different water than small S. Am. tetras>

..bought it sick, had a fungus I didn't notice, from the store with a no return policy and couldn't cure it. Freshwater tanks not advised :( ) .
<Ah yes>
 I'd like to replace them but I'm looking for a more colorful version. Here's the hitch. I have a red tailed shark (no I don't plan on returning it) and I can't seem to find much information on compatible species,
<Pterophyllum/Angels, Gouramis, mid-sized barbs, danios, Rasboras... Rainbowfishes... many choices>
ones that are fast enough to dart away without injury but are also mostly calm fish when they are not being harassed. I refuse to try stocking Glofish(or their unaltered counterparts-Zebrafish) again...that was a nightmare. My shark isn't terribly aggressive and is approaching 3 years old and I believe it to be female. Mostly she hides in her corner cave, hates people looking at her closely but will randomly come out and give the free swimming fish a chase or two around the tank before going back into hiding. I also have an Oto
<Otocinclus are social species; see WWM re>
 whom the shark loves, it's allowed in her corner all the time. The tank is clean test wise and middling pH 6.8, but very hard in GH. I'm looking for a species or two around 2 inches when mature and while I will restock with more of the phantoms and skirts if that's all she'll tolerate(they seem to be good mates), I'd like to try some more colorful versions like lemon tetras, cardinal tetra and red phantom tetra?(no “painted” fish please)
 I was considering Neon tetra but in reading they sound stupid and slow when it comes to being pursued by other fish. I will research on top of any suggestions you can make for species but having a place to start beyond the ones I had would be nice.
Thank you so much,
<I'd skip the Tetras... Read here: http://www.wetwebmedia.com/FWSubWebIndex/rtsharkfaqs.htm
Bob Fenner>

Redtail shark chasing rosy barbs      6/3/12
Hi, I have been in the aquarium hobby for four years now.  I upgraded tank size every year.  Now I have a 60 gallon show tank, which is 4 feet long, 13 inches deep and almost 2 feet tall.  I have had this tank for 8 months.  It has 3 long veil angels (that are 2 years old, so big and beautiful), 5 long finned and 4 short finned rosy barbs (3 years old), 12 Rasboras (almost a year old), a Corydoras nanus that is four years old and three peppered Corydoras (6 months old), five blackskirt tetras (three years old), two Bristlenose Plecos (one year old) and one redtailshark (4 months old).  The reason I am giving you their age is because I want you to know that these fish have been living peacefully together with no fin nipping.
<Real good.>
All your conversations about rosy barbs include fin nipping and I have never seen my fish bother each other.
<If the comments were mine, they'd be about Rosy Barbs being nippy at times. Not all Rosy Barbs nip at their tankmates, and those that do, usually do so towards slow-moving fish, such as fancy Goldfish (being subtropical rather than tropical fish, Rosy Barbs, there's the potential there to mix them with Goldfish).>
It may be that my angels are so big that the Rosies and the blackskirts won’t try anything because of that.
<I see. Do be aware that Rosy Barbs can get to a fair size, though aquarium specimens do seem to top out at 8-10 cm, versus 15 cm in the wild.>
But I recently (three weeks ago) added two small angels and no one bothers them either.  My question is about my Redtail shark.  When I introduced him, he entered the tank slowly going down, looking everywhere and making his presence known; a real shark!
The other fish looked at him but didn’t get close like they knew HE was a shark.
<Well, not sure that's really what happened, but anyway…>
My Rosies are really curious and they usually go see who is new but they didn’t with him.  It was cool to see the hierarchy in the fish!  Anyway, he was peaceful and hiding before but since about a week, he has been chasing my rosy barbs all over the tank.  I am wondering if he will stop that behavior when he gets bigger than them.
<Possibly. Red-Tail Sharks essentially view anything of similar size and shape as a rival, and chase it away. That's why they're often fine with Angels but less good with barbs or danios. Sometimes Red-Tail Sharks do indeed settle down and all is well.>
They are about the same size right now but I know he will get bigger.  I had read about sharks before buying him because I wanted a compatible shark.
<An unreliable choice in this case. The Rainbow Shark is generally less aggressive than the Red-Tail Shark, though I admit, there isn't a huge amount in it!>
He was described as the kind that would go in my peaceful tank and he was in the beginning.
<Definitely not! Red-Tail Sharks are not "easy" community fish by any means.>
Now my Rosies keep to the top half of the aquarium when they used to swim all over.  Will things improve or get worse? 
<Impossible to say. Your tank is only just big enough for the Red-Tail Shark (they hold territories that fully occupy 50-60 US gallons). With luck, the Rosy Barbs will settle down and learn what part of the tank is theirs, and the Red-Tail Shark likewise. But no guarantees! You could try removing the shark, moving the rocks and plants about, and then after 20 minutes or so, putting the shark back. Sometimes that resets the hierarchy and minimises bullying. While you're at it, if your shark has a favourite cave, move that cave into a corner, and break up lines-of-sight as best you can with tall rocks and plants.>
Thank you for your time.  Nicole
<Welcome, Neale.>

Red Tailed Shark behavior 1/30/12
I have a 40 gallon tank with one RTS, 2 mollies, 2 Sword Tails, a crayfish (small Florida Blue type) and 3 Danios plus snails and sucker cats. The RTS is happy, black and looking healthy. My question is behavior. I have found him happily floating upside down under a large piece of driftwood (there are lots of nooks and crannies in my driftwood setup). He/she comes out to chase others away occasionally, then goes back upside down and hanging out. I got him/her before the white tips showed up and only about
1 1/2" long, so I doubt it is laying eggs, but??
<Nope, not spawning.>
I have also noticed other people asking the same question on other sites, but no one seems to have an answer accept that the fish is ill. I assure you my water parameters are good and he/she looks healthy. Any idea what its doing?
<If he is able to swim around normally, but only rests upside-down with his ventral surface pressed against a solid object -- that's normal! Once they have found a suitable cave or tunnel, they swim into it and rest with their belly against the surface of that cave or tunnel. If that means they go upside-down, that's what they do! Cheers, Neale.>

RT shark... beh. 1/11/11
Dear Crew,
I just bought a red tailed shark yesterday. After about an hour after acclimating he seemed fine swimming about the tank like a normal fish.
Later that evening when I went to go turn the light off I watch him for a while to see if he was doing fine. He was swimming perfectly and then I saw him or her twitch. Is this normal? He/she does it sometimes but that's about it.
Thank you,
Dante G.
<Some twitching is natural, not a worry. Bob Fenner>

Aggressive Red-Tailed Shark 10/13/10
Dear WWM Crew member,
I need your suggestion on this. The Red-Tailed Shark in my one tank is becoming more aggressive day-by-day.
<This is what they do.>
These days he is chasing all the fishes including mollies and swordtails. I read that Redtails are aggressive towards only males of same species, but I never thought of this.
<Hmm'¦ it is generally widely known that Red-Tail Black Sharks are territorial and aggressive. In aquaria smaller than 210 litres/55 US gallons they are usually very troublesome.>
Please tell me can I keep the Redtail solitary in the tank. May any problem arise if it is kept alone [with no other fish].
<Red-Tail Black Sharks are most aggressive to fish of similar shape. They work best with catfish that stay close to the bottom of the tank and small schooling species like Danios they don't register as threats. Moderately aggressive cichlids can work well, but there will be aggression between them over hiding places, so the cichlids need to be of comparable size to the Shark, and the aquarium must be big enough for both species to claim territories of their own.>
Thank you for help.
<Do read here:
Most problems with this species come from keeping them in a too-small aquarium. Cheers, Neale.>

Re: Dead Sailfin Molly, Now Red Tail minnow shark colour: hlth./beh... 8/22/10
Dear Neale,
<Hello again Deeptam,>
Thank you for the advice. I am sorry for the mistakes you have mentioned and have been trying to correct them. However the molly tank I mentioned is not freshwater but brackish, as advised in your article. I forgot to mention that.
Thank You again and I would like to request you to kindly look at the photo of my red-tail shark [photo attached]. Its fins are showing increasing white area. Is this normal?
<Yes. Some specimens do have white or grey edges to their fins. Provide there are no signs of fraying or Finrot, don't worry!>
Except this its a very active and healthy fish [at least appear so].
<Does indeed look healthy. Be careful with seashells in the aquarium though. These can raise the pH and hardness.>
Thanking you
<Most welcome! Cheers, Neale.>

stop red-tail shark aggression... Mis-stocked FW 8/6/09
I have been told I have a messed up tank because I have 2 goldfish (a black moor and a fantail) as well as white mountain minnows a molly a swordtail and a Pleco. I gradually changed the water temp so the goldfish would adapt
before introducing the molly, swordtail etc.
<Well, not good combinations, that's true. Mollies in particular do best in slightly brackish water, making them difficult to combine with other species.>
about 4 weeks ago I introduced 2 green tiger barbs and a red tailed shark (about 1 and a half inches) to the tank. the barbs immediately started harassing the black moor so I removed them, and everything went back to
normal. that was 2 weeks ago.
<Please, please, please research fish *before* buying them.>
at feeding time this morning I noticed a few stray scales on the black moors body but didn't think to much of it, but as the day went on I noticed his tail is all shredded and more scales have been removed. that's when I noticed the unusual aggression the red tail is showing towards him. it seems to be beyond just territory because the red tail will hunt him out wherever he is in the tank without letting up.
<Again, please research your fish. Red-tailed sharks need big tanks (I'd say upwards of 55 gallons) and are very aggressive towards other fish of similar size and shape. They certainly shouldn't be kept with Fancy Goldfish which can't swim fast at the best of times, let alone when being chased by something aggressive.>
I know red tails can be aggressive but why would this behaviour start only today?
<It takes a while for a fish to define its territory and determine whether it can be the dominant fish in this community. Your Red-tail Shark has decided it can, and so it's become aggressive.>
is there any way of stopping this behaviour or maybe a way to change who he takes his aggression out on?
I have a few caves set up, but he doesn't seem to stay in them, instead he has been on constant search mode since I got him.
<Depends how big your tank is. In a 200 gallon tank for example, a Red-tail Shark will usually claim just one half of the tank. But in smaller tanks, it essentially views the whole thing as its home "turf" and will drive away anything it deems a rival.>
I have removed the black moor to my quarantine tank but I would rather keep him in my display tank if I can.
also I'm thinking of adding a Gourami and a Betta, is this a bad idea?
<Well, obviously, yes. Until you've fixed this problem, why add more variables? A Betta in any case will likely be shredded by an aggressive Red-tailed Shark, and unless the tank is very big, Bettas and Gouramis often don't get along.>
many thanks,
<Cheers, Neale.>

Re: new 125 high and possible multiple red-tailed black sharks? 4/6/2009
Hello again, after reading all I could about red tailed black sharks I bought 5 (4 with my b-day present gift card, one given by the store for my b-day lol) of them for my 125 gallon high tank. It has lots of cover,
rocks, plants (fake) and wood. My question is, about 24 hours later, the 3 that were in one bag for the journey home are still hanging together, two of them frequently swim side by side bumping each other ( I did notice a VERY little bit of aggression, charging, at feeding time this morn). I am wondering what the side by side bumping behaviour signifies, is it testing for dominance, mating, or something else?
<Too small for mating... but likely play leading to dominance at work here>
Anyway, I do expect all 5 of the fish to eventually claim and aggressively defend territory.
<Me too>
Thanks for your time again.
<Welcome. Bob Fenner>

Red Tail Shark Barrel Rolls 3/1/09 Hey WWM, I've had this red tail shark for over 4 years and he has been swimming in barrel rolls since this morning. He was originally in a 40 gallon tank, but kept attacking my Bala, which he lived with for 4 years, so I moved him to a 20 gallon tank by himself. He's been there for about 9 months and has done good since the move. He has always acted a little weird, like propping himself tail down against a rock or outside the cave. Most of the time he hides in a large dark cave. This barrel roll behavior is definitely new. I checked the water, which was a little basic, so I did a 20% water change and added 2 tbsp. of aquarium salt. I checked back every 2 hours and have noticed little change. He's not running into walls, and he can trace the perimeter of the tank without rolling, but when he gets to open water, he begins spinning. Any ideas? Thanks, Josh <Hi Josh. When fish go "loopy" it's often caused by a sudden change in water quality or chemistry. So since you've also detected a change in pH, this is what I'd study carefully. If you're using "salt" to control water chemistry -- you're not! Sodium chloride does precisely nothing to pH and hardness. Do see here: http://www.wetwebmedia.com/FWSubWebIndex/fwh2oquality.htm http://www.wetwebmedia.com/FWSubWebIndex/fwsoftness.htm Cheers, Neale.>

Can Puffers live with Sharks... FW 7/1/08 I just got a new aquarium last week (I caught the water fever must have more aquariums Lol). It is 10 gallons and has been running for the past 3 or 4 days. I have some plastic plants in it and a rock cave. I really like Dwarf Puffer fish and used to have one in a 5 gallon tank. I want to get another one and keep it in my new tank with a red tailed shark. I know that they are both aggressive species so because of that will they tolerate each other. I am not going to put anything else in the tank other than them. If I get them should I get another cave so they can each hide in their own? I have extensively researched both species and still can't decide if they will be compatible. Also will a Dwarf Puffer harm a large snail? Thanks for any reply! Your website is great and I have found a lot of useful information on it regarding fish and turtles. Keep up the good work. -Amanda <Hello Amanda, and thanks for the kind words. The short answer to your question is NO, this combination won't work. The most likely outcome is that the Dwarf Puffers will nip at the Red-tail Black Shark. Adult Red-tail Black Sharks also need MUCH more space than 10 gallons, so unless you (at least) quadruple the size of the aquarium, you couldn't fit one in. Furthermore, Puffers eat snails, and so any snail put in the tank with them will simply be viewed as food. Small snails are eaten whole, big snails a mouthful at a time. The best and most reliable approach is to keep Dwarf Puffers on their own, either singly or in groups, with ~15 litres/4 gallons per Puffer. Hope this clears things up! Neale.>

Red Tailed Shark is Looking Quite Ill 4/5/08 Hello Crew! My Red Tailed Shark has got some very concerning symptoms I need help with... 1.) Both eye's have a bluish film on them, it appears to be growing from the center and working its way out. 2.) Mouth has a white crust on it. 3.) He is pretty much outlined in white. Like there is a thin white silhouette around him. 4.) He is lethargic, and gasping at the surface... Now, he did undergo some stress yesterday. I was trying to catch my three Black Tetra's to put them in another tank, and that proved to be a stressful event for the other fish. Also, my wife decided to redecorate the tank the same day (great timing). I added some stress coat, and changed the filter media also. So any idea what is wrong with him? What should I do? Regards, Ben <Hi Ben. Almost certainly either Finrot, Fungus, or Mouth Fungus, and quite possibly a combination of two or more. There may also be heavy mucous production, and that would explain things like the cloudy eyes. These diseases are all caused by poor water quality almost always, so check that. Treatment needs to be immediate: use something like Maracyn or eSHa 2000. Don't wasted your time with Stress Coat, salt, Melafix, or any of these nonsense products. Make sure you remove carbon from the filter when using medications. Cheers, Neale.>
Re: Red Tailed Shark is Looking Quite Ill 4/5/08
Thank you for you quick response Neale! Unfortunately, my Red Tailed Shark didn't even make it through the night, so I couldn't try the medication you suggested. <Too bad.> Bummer, as he was the Elder Statesman of my tank. I have NEVER tested my water before, and have had tremendous success over the 5 or so years I've been running my tank. <We're all guilty of this, at least on the freshwater side of the hobby. But still, I'd heartily recommend buying a pack of "dip strip" multipurpose testing strips. These may not be the best in terms of accuracy but they're economical and useful. It's worth testing the water in a mature aquarium at least once a month, just to make sure everything is ticking over nicely.> This was the first sick fish I've ever encountered. But I did go out and buy a test kit last night and discovered that my water is quite hard, and my PH is off the low end of the chart. <So it's hard but acidic? Quite an odd combination; what it essentially means is that the water contains a lot of minerals, but not many of them are ones that raise pH. In other words, the general hardness (degrees dH) is high, but the carbonate hardness (degrees KH) is low. Are you drawing water from the tap or from a domestic water softener? Remember: the water from a domestic softener is not recommended for fishkeeping.> It's odd, because I felt my tank was very stable. Will adding chemicals be required on a regular basis to build my PH level and drop my water hardness? <If you can, avoid modifying the pH of the aquarium. If you want to raise the carbonate hardness, that's fine. But changing the pH directly is usually more trouble than it's worth, and not something I recommend. Much better to determine your water chemistry out of the tap (but not the water softener) and then choose fish that prefer or happily adapt to that set of water chemistry conditions.> Once I have build adequate PH, will it sustain it's level, or will I always have to add chemicals? <Once you start messing about with pH, it becomes a constant job. That's one reason I recommend against it. Do see here: http://www.wetwebmedia.com/FWSubWebIndex/fwh2oquality.htm  http://www.wetwebmedia.com/FWSubWebIndex/fwsoftness.htm  http://www.wetwebmedia.com/FWSubWebIndex/fwhardness.htm  >
Regards, Ben <Cheers, Neale.>

Red-tailed shark in a 10 gallon tank, bad behaviour (quelle surprise) 2/3/08 Hi WWM crew, I have a 10 gallon planted tank with 5 mature guppies and 4 adolescent ones, and 1 red tailed shark. in the last few days ive noticed that my shark has gotten a lot more aggressive and active so I was wondering if you guys could tell me whats wrong with it, I'm not sure if its a male or female but I've been told that its a female because her dorsal fin is curved not pointed. <Hello Marco. A Red-tailed Shark (Epalzeorhynchus bicolor) is completely unsuitable for a 10 gallon tank. Even a 40 gallon tank would be borderline for this fish. It gets to 15 cm, is highly territorial (regardless of sex), and is very active, to the point many specimens die by jumping out of the tank. So this fish needs to be re-homed, ASAP. There is no chance this fish will EVER coexist with Guppies in a 10 gallon tank, period, end of discussion. Please do take the time to read up on a species before purchasing it. Many (most) of the fish widely sold in aquarium shops have special needs of one sort or another, and cannot be randomly added to any aquarium. The advice from aquarium shops is variable, and does rather depend on you being honest to the clerk about your fishkeeping skills and the size of your tank. No reasonably well trained clerk in a fish store would ever recommend mixing Epalzeorhynchus bicolor with fancy guppies in a 10 gallon tank! Cheers, Neale.>

Re: red-tailed shark in a 10 gallon tank, bad behaviour (quelle surprise) 2/4/08 Thank you for the advice. is it ok if I move it with my dads 50 gallon tank? he has 7 goldfish and 2 tank cleaners all over 5 inches. <A Red-tailed Shark could be kept in a 50 gallon tank without problems. The tank does need to be *tropical* though, not less than 24C, which isn't how Goldfish are normally kept. I'm also concerned about the "tank cleaners" Apart from the point that no fish cleans the tank (that's your job) and all fish make the tank *more* dirty, it isn't clear whether you are talking about a Plecostomus-type catfish or a "Chinese Algae Eater", Gyrinocheilus aymonieri. Red-tailed Sharks WILL fight with Chinese Algae Eaters, and vice versa. As a general rule, all the "shark" type minnows are territorial and mutually aggressive, whether Labeo, Gyrinocheilus, Epalzeorhynchus, Garra, etc. If the Chinese Algae Eaters are bigger than the Red-tailed Shark, they will chase and possibly kill the Red-tailed Shark. Gyrinocheilus aymonieri is one of the least pleasant fish in the hobby, and not recommended for home aquaria. Cheers, Neale.>

Rainbow Shark, Red-Fin Shark, Compatibility Hi! My name's holly! I recently bought a shark (I'm not sure what type of shark it is) with red fins (ALL the fins are red) and a red body. I thought it was a red fin shark but I'm not to sure...I was wondering if you could tell me what it is. So when I got it, it did nothing but hide in a little cave of wood that I have in my tank and it wouldn't eat. I got worried so I bought a red-fin shark (I am sure this one IS a red-fid shark) to try to make him come out and eat and maybe be a bit more active. I think it has worked but I'm not to sure. I can see it eating now...should I still be worried? If so what can I do and was adding another red-fin into the tank a good idea? If it makes any difference I have a community tank and I have: 1 x clown loach 1 x snail 2 x neon tetra 2 x white cloud 2 x big sucker fish 3 x tiger barbs 5 x platies (and the 2 I'm asking about) <Hello Holly. The fish you bought are Epalzeorhynchos frenatum, also known as the Rainbow Shark. This is an aggressive, territorial omnivore from Southeast Asia. Feeds primarily on green algae and tiny invertebrates in the wild, but in captivity does well on algae, algae wafers, small live foods such as brine shrimp, etc. These fish tend to be pretty belligerent towards one another, so adding two specimens isn't a great idea unless you have a really big tank. So if possible, re-home that fish. Yes, they mostly hide in caves, except when out feeding or chasing rivals. Dissimilar fish are generally ignored. For some reason you aren't keeping your schooling fish in schools. Neons, clown loaches, minnows and barbs all should be in groups of at least 6. With clown loaches, you can get by with fewer, but they're shy. By the way, Clown loaches get big: up to 30 cm. "Big sucker fish" can mean anything, but I'm assuming those are either catfish (Pterygoplichthys spp, which grow to 30-60 cm) or "sucking loaches" (Gyrinocheilus aymonieri, to 30 cm, and incredibly nasty and aggressive when mature). Both need giant aquaria (300 liters +). There's plenty more info on "sharks" here -- http://www.wetwebmedia.com/FWSubWebIndex/minnowshks.htm . Cheers, Neale>

RT shark comp... incomp... 7/11/07 Hi <Ave!> I am writing to ask about my red tail shark I have him in a tank with an angelfish 3 neons and one guppy. He is a lovely fish but he bully's the tetras and guppy a lot chasing them and nipping their fins and tails, the guppy's tail is starting to look a bit of a mess. <Unfortunately absolutely normal. Red-tail Sharks are legendarily aggressive given their fairly modest size. In a 55 gallon tank they're usually fine, and burn of their energy swimming about, but in anything smaller they tend to become little tyrants. There's nothing, unfortunately, you can do. Guppies, neons, and angels are all fairly docile, slow-moving animals and they just can't swim away from the RTS fast enough. If you're choosing tankmates for an RTS, you want high-performance animals like barbs, rainbowfish or silver dollars. They also work well with semi-aggressive but non-predatory catfish such as Plecos, Synodontis, Hoplosternum, etc.> I've recently managed to get a smaller tank my plan was to move the tetras and guppy into it and then add a betta, to give them a bit of peace. <Sounds a good idea. Do be careful about the Betta though: neons have been known to nip at Bettas. I'd tend to suggest you buy a *female* Betta as they tend to work better in community tanks, having shorter fins and so being able to swim more efficiently.> The only thing I was worried about was if I remove them will the shark have nothing to realise his aggression on and will he become aggressive to the angelfish? <Entirely possible. On the other hand, when the Angelfish matures, it'll view the neons as food, so keeping them together might not be an option, either.> And also my second question is that if it would not be a problem removing the smaller fish please can u recommend a medium sized fish that will not bother my angel fish and will not be bothered by the shark. <Depends what you want. If you want midwater, schooling fish, then Australian rainbowfish are hard to beat. They are very very hardy, totally peaceful, and live for years. So while a bit more expensive than barbs or tetras, they work out as very good value. If you're looking for something a bit more characterful, then a catfish like Hoplosternum littorale is hard to beat if you have the space. They're ugly as heck, but easy to tame and can even be hand fed. Practically indestructible animals, that short of being baked in the over for 20 minutes will survive most things. But they're quite big (around 8 inches) so not for the small aquarium. If space is tight, then Corydoras would be a good call. A group of these will coexist nicely with your fish and should be ignored by the RTS. The main thing is to avoid anything that *looks* like a shark, i.e., no Flying Foxes, Loaches, Torpedo barbs, etc.> Thanks <Cheers, Neale>

Red-tail shark, Repro. beh.- 03/25/07 Hello, I have just recently found your site and have found it helpful. I have a 125 gallon tank. I have lots of live plants and some large fake plants, a large wood root and some other items... I have lots of cover and hiding some large open areas. ok my questions. I have 6 red-tail sharks, 6 tin-foil barbs, 2 clown loaches, 3 algae eaters, 2 Plecos, 8 tiger barbs, 1 peacock eel, 10 misc platys, 3 silver-tip sharks, 4 pictus cats, and one other not sure of the name but is really cool looking.... ok everything gets along believe it or not... all has there own little areas. I have tried to do a lot of research on red-tail sharks breeding, but have only found that there is not much known on the breeding habits. <Actually... are cultured... brought into readiness by environmental and hormonal manipulation (injection)... More of a trade secret than unknown> I have found lately that 4 of my 6 have seemed to pair off about once a month and will seem to have a little aggression toward each other by a little fin nipping and chasing each other around the tank, <Typical behavior for the species> then they will touch bodies with each other facing the same direction just a little offset (one just slightly back so their fins stack on each other). then while pointing at about 45 degrees, they start waving back and forth while touching each for about 20 to 30 seconds and then it starts all over again... this happens for about 5 days from what i have noticed. I haven't seen any eggs in the tank, however with all my fish they could quickly be eaten. I have been wanting to video this action... just not sure if they are trying to breed or not..... thanks for any info you may have <Does read like spawning behavior... are these fish large? Like six inches or more? Perhaps just a "teenage" phase at this point... Bob Fenner> Brad A. LaRose

Re: Red-tail shark, Repro. beh. 3/26/07 No only about 2 1/2 some still have the white tip on the dorsal fin. <Ahh... still juveniles... need to be about four inches Standard Length (w/o the tail, ending at the hypurals)... about 4.5 to 5" Total Length before sexually mature... BobF>

Gouramis and Red Tailed Black Shark 1/19/07 Hi! Pip from Worcester England here! I'm just curious as to why my Red Tailed Black Shark keeps eating the slime off my Blue and Red Dwarf Gouramis? <Nutritive> She doesn't do it all the time, but more often than she used to. Will she stop it? <Unfortunately not likely... and is destructive> The reason I ask that is I have a Male Betta in the same tank and he used to pick on my Gouramis when they were first introduced, nipping their fins and displaying to them, and when I asked at the aquaria shop what I could do about it, the gentleman I spoke to told me not to worry, that it would stop. <Mmm, generally not a problem... as the smaller gouramis are aware of the Betta kin's propensity to do this... will/can avoid it> Sure enough, it did and they've been fine ever since. It's a 36 inch tank, so it's not exactly small and there are plenty of plants and hiding places, and they are all fed a varied diet, though the gouramis and shark do like the algae tablets that I put in, and I notice the slime eating happens more at meal times, especially when there is an algae tablet in there. Could she be trying to get them to leave it alone? <Mmm, not really... as stated the minnow-shark derives nutrition/food from such activity... May also be a bit of an agonistic/territorial display... but whatever the "reasons" this activity damages the Gouramis... if too much... I would at least try adding some "dither-fish"... perhaps some small grouping of barbs, danios... to "draw off" the attention of the RTS here. Bob Fenner> Red tailed sharks and Goldfish tog. Dear Sir, <<Hello, Lara. Tom with you.>> I read your article about red-tailed sharks online. It was very interesting and informative! <<Wish I could take credit for that one, Lara. Glad you liked it, though.>> I used to have a red-tailed shark in a regular aquarium years ago. <<A very nice fish, to be sure. A little tricky to get appropriate tank mates, however.>> I was wondering if I could keep one in a tank with goldfish? <<The problem here, Lara, is that it might work and it might not. Seems a bit noncommittal, I'm sure, but I'm from the 'school' that doesn't believe in mixing other species with Goldfish. The 'safe' answer would be, 'No', but sometimes one can be too conservative. Red-Tails are territorial and can be a bit nasty with small fish. Goldfish don't pose this problem, size-wise. Red-Tails aren't 'fin-nippers', per se, though their behavior can leave you with this impression. You don't mention what type of Goldfish you have (and, I assume you already have these) so I would advise the following. If you have a 'fancy' variety of any sort, don't go with the Shark. These Goldfish would be slow swimmers and, perhaps, the subjects of aggression from the Shark. If you have Commons or Comets, it might be worth a try. These will grow large and Red-Tailed Sharks do better, behavior-wise, with larger fish. A lot of this will depend greatly on the size of your tank, the number of fish in it, the water temperatures (should be mid-70's F. if this is to be successful) and, ultimately, what you're prepared to do if things 'go South'.>> I heard that goldfish need to be in aquariums full of goldfish only. <<By and large, Goldfish have different requirements than other fish do. They're adaptable to much colder temperatures than tropical fish are, for one. They require much larger tanks than the majority of hobbyists think they do. For example, I wouldn't place a single Goldfish of any variety into a tank of less than 30 gallons. They're 'messy' and place a very sizeable bio-load on a tank which is a big reason for large quarters. Small tanks simply don't provide enough 'stability' where water conditions are concerned. Diet is another factor. Goldfish don't process proteins well. A huge reason for problems like Swim Bladder Disorder and constipation. Red-Tailed Sharks, though scavengers by nature, are omnivorous where Goldfish are largely herbivorous. Something to keep in mind if you go through with your plan.>> Thank you for answering! Lara <<I think I've given you enough to go on, Lara. If you have anything specific to ask, I'll be here. Best regards. Tom>>

Red tailed shark as babysitter? - 05/13/2006 Hello! Before I ask my questions, let me just say that I'm really enjoying your site...I've been reading through the FAQ's and find them very informative. <Thanks for stating so> I recently set up a 20 gallon aquarium (for it's calming effect) <Heee! Aquariums are (or seem to be) only calming to non-owners!> and everything (plants, snails, fish) is thriving. I woke up one morning to discover fry...and thought "How cute!". Then one fry was eaten. Needless to say, the relaxation part of fish-keeping flew out the window as I couldn't catch the fry to remove them to a smaller aquarium (they hid in a cave and among the plants). So, I boiled aquarium rocks to make more fish caves, bought more plants for the fry to hide in, etc. I also bought a liquid fry food, which all the fish seem to love (they're all still quite small). I don't know how many fry there were as I only ever saw two at a time, but two have survived... because of the red tailed shark. He's become the fry-sitter. Have you ever heard of this? <Mmm, no... Neat!> The little shark took over a large cave, and he allows the fry to 'hang out' with him. He chases the other fish away whenever they come close, <This part is very common though...> thus keeping the fry from being eaten. At first I thought he (or she) might be keeping the fry for his own dinner, but no. The 2 fry are about 4 weeks old now, and they're getting quite big. They swim about freely...with the shark. I've Googled 'red tailed shark' as babysitter but needless to say, found nothing. Is this weird, or does the shark think the fry are his/hers? <Don't know... but these "minnow sharks" don't display parental care behavior with their own in the wild or captivity...> Also, I just bought a 35 gallon hex tank, and I'm going to transfer some of the fish there. If I put some of the filter material and water from the established aquarium into the new filter and aquarium, will it cycle more quickly? <Yes. Please read here: http://wetwebmedia.com/FWSubWebIndex/fwestcycling.htm and the linked files above re> I'm just wondering how many fish at a time I should transfer after the water is ready. <Try a few, test the water... move a few more in weekly intervals...> I also have a large tank, 80 gallon, I think, so if these fish keep reproducing I'll be ok. I haven't set up the large tank yet though...I can't lift it by myself to put it on the stand. <Do get some (strong) help here... watch your back!> Sorry for going on so long! I look forward to hearing from you. Take care! Kathy <Thank you for writing, sharing. Bob Fenner>

Suddenly aggressive Red-tailed Shark 10/17/05 Hello, <Hi there> I have a 20 gallon tank with 1 male Betta, 2 spotted Corys, 1 red-tailed shark and recently added 3 gold barbs. I had never had any aggression with my red-tailed shark but when I brought home the 3 gold barbs the shark has grown more aggressive. <Yes... happens... and more often with interaction with other cyprinids> He constantly chases the barbs until he himself is exhausted or bored and occasionally gives a brief chase after the Betta and Corys. <Can't likely harm the barbs or Corydoras, but the Betta...> The barbs hang around the bottom of the tank gasping from swimming so much and hide in corners until the shark comes by for another round. Everything I have read says red-tailed sharks are normally compatible with barbs so I'm rather shocked to see him act this way. <As stated... happens.> He has plenty of caves and cave like areas to call home and the barbs are not normally in these areas unless the shark chases them there so I'm not sure why the shark is doing this. He doesn't appear to be actually biting them just chasing them and occasionally when they all get bundled up in a corner he accidentally "or for all I know purposely" rams them. How can I fix this problem and what may have initiated it? Thanks in advance Lynette <Likely "breaking up the environment" a bit more will reduce this apparently agonistic behavior (if the tank itself is large enough... at least 29 gallons let's say). I would provide some floating "bunch" plants... these are listed on WWM, for the barbs to hide in, all to eat at their leisure. Bob Fenner> <<These fish have been observed living quite comfortably (holding their own) in tanks with very aggressive Neo-tropical cichlids. Marina>>

Red tail shark swimming funny 9/1/05 Hello.. I have a fairly new tank (almost a month) and have had the water levels checked, and everything appears to be in order. I have 2 Dalmatian mollies (new to fish so not sure of the sex), and a male betta, and a red tail shark (again not sure of the sex), I started with the mollies, 2 weeks later added the betta and then the shark. The red tail shark hides in any caves he can and stays there ALL THE TIME. He doesn't come out to eat. I just fed the fish and noticed that he wasn't coming out of his cave, so I picked up the cave and shook it around (he usually comes out when I do this, but doesn't eat), today he didn't come out and was swimming on his head upside down and would roll around so he was right side up and is continually moving around in this manner with all fins moving. Should I be worried? <Yes> It was almost like maybe I made him dizzy when I was trying to shake him out of the cave to feed him . Please help. Would you suggest that I buy another so he has a friend? <No... too likely to fight> He is the shy/ anti-social bunch. The other three seem to get along fine. There is some chasing, but they seem happy. I think I have a female molly and the betta and other molly I think are males. I was going to go to the fish store where I bought them and have them check my water levels again. Any idea what is happening to my shark?? <Possibly just getting used to the tank... maybe doesn't like the type of food you're offering... perhaps is eating when you're not observing... I would just be patient here. Bob Fenner> F.Y.I. I finally got the shark out of its hiding place and noticed 2 small dark spots (like another set of eyes ) near the head of the fish. what does this mean? Is this why he/she is swimming funny?? Jenn <Likely just the natural markings of this species... easier to see when the fish is frightened or when the lights have been off for a while... Bob Fenner>

More than one red tailed shark? 9/1/05 Hello again. Quick question. I have a 108 gallon and have among other fish six "flying foxes". I just purchased a red tailed black shark about 1.5 inches. Settling in ok but have found him to be chasing the foxes now and then. Being similar in shape I understand why. Everything I've heard about this fish is to keep one specimen. This tank is heavily planted and I was wondering if I could or should keep a small school to stop the aggression toward the foxes? Could this work and what would you consider to be an acceptable number in this particular tank? Leave as is or more sharks? Your advice is the best out there!!!............Tanks a lot..............Craig P. <It is a very territorial fish, that will be more aggressive as it matures. You can keep the sharks in a small group when they are young, but it will be increasingly difficult as they mature. I would stick with one, unless you want to add 3 more and remove them as they get older and more aggressive. Good Luck, Oliver >

Red tail sharks I have three red tail sharks 1 is big and the other small, My smaller ones are doing fine but my big is unusually is has a dark coloration nears it gills and for two days it was extremely big and no it is thinner but has a blackish colour by its gills all of my other fish are doing fine except for these one. <Alas, the symptoms are not very specific for diagnosis...please test overall water chemistry and look for deficiencies. Feed medicated flake food for precaution if you feel it is pathogenic. Anthony Calfo>

Red Tailed Shark A few days ago we noticed that our red tailed shark's bottom lip is protruding grotesquely and is bright red, he is hanging vertically headfirst at the top of the tank. He obviously is not feeling good. Coincidentally, or maybe not so coincidentally, we have a bacterial infection running through our angels right now, which has resulted in 7 deaths since Saturday. We are treating them, since Monday, with Nitrofurazone. Any ideas as to what the problem may be, and should we euthanize him and put him out of his misery? Thanks. Zak Barrett :'( < Do a 30% water change every day before treatment and make sure the filter is clean and the carbon has been removed . This will make the medication more efficient. You shark does indeed have a bacterial infection and the medication should have some effect. If the mouth does not heal properly then he may not be able to eat. If he survives the treatment watch him to see that he gets enough to eat. If the mouth is damaged beyond repair then put him in a glass and add a couple of Alka-Seltzer tablets. The co2 in the tablets will displace the oxygen in the water and your fish will slowly drown.-Chuck> Unusual behavior or RT Shark I have a guppy tank with 10 half inch guppy fry. My red tailed shark (2.5 inches) seems to be acting very strange. He sort of chases the guppies from his cave but he does this flicking thing, like he bolts for about 4 inches very quickly, turns sideways then swims to the bottom. also he does this when there's no other fish to chase. My red-tailed shark also seem to like to be cleaned by the guppy fry. He'll lay on the bottom and the guppy fry will well pick on him like cleaning him. Is any of this behavior seem strange to you or the "flicking thing" unusual? <Not unusual... normal... but there is a concern going forward re compatibility... the Shark will likely cause your guppies trouble as it gets larger> P.S. my tank for the freshwater barracuda (Ctenolucius hujeta) is 49 gallon tank that my cichlids used to be in. will this tank be ok and do I need to make any water adjustments? <Likely will be fine. Bob Fenner>

Colorless minnow sharks I have a 30 gal tank with 3 balas and 3 redtails (1/2 in each) and two of the three redtails actually are lacking color in their tails. Is there any particular reason for this? <Three principal possibilities (or a combination thereof)... Genetic... some are just not from colorful stock Nutritional... not fed enough of what it takes to color up Environmental... water conditions don't suit them. Likely yours are just young... will color up given your good care, a mix of foods (some fresh, some green) and regular maintenance (water changes...). Bob Fenner>

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