# Red-Tailed Rainbow Shark and Cory Cat Compatibility?



## AquaHobbyist (Jun 8, 2016)

Hello everyone,

I just bought a red-tailed rainbow shark a couple of days ago as it was suggested by one of my friends that it will help with keeping algae at bay. Currently I have a 20 gallon tall, with lots of plants and a big piece of driftwood that is big enough to hide both pleco and rainbow shark (it's more of a tiered piece of wood). 

As for fish, I have 5 danios, 2 albino corys, 2 julii corys and 1 albino bristlenose pleco. 

I've read that rainbow sharks can be aggressive to their own kind, but have read mixed articles regarding their aggressiveness towards other fish. On forums I have read that some are aggressive towards other fish, some are peaceful and keep to themselves. 

I make sure that when I feed the corys I drop enough food for all the bottom feeders, as I know the shark may compete with the corys and pleco for food. So far, I haven't seen aggression against the corys or the pleco, though I have seen it nudge the corys every once in a while during feeding time. Corys and pleco are acting normally and seems to not be in any distress, very active and swimming about without any change in behavior. The rainbow shark mainly swims around nibbling on algae on the plants. Of course, this is only the third day so not sure how things will play out in the long run. Rainbow shark is about 2 inches.

Still, I would like to get opinions on the compatibility of the rainbow shark in my tank with its tank mates. Any feedback would be greatly appreciated! Thanks!


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## bigbadjon (Aug 6, 2015)

Is it a rainbow shark or a red tailed shark? Mine briefly chases most of its tank mates but I've never seen it beat anything up.


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## AquaHobbyist (Jun 8, 2016)

It's a red-tailed shark. Sorry for the confusion.


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## bigbadjon (Aug 6, 2015)

Mine is a rainbow shark. I hear the red tailed sharks are more aggressive but I've found that aggressiveness in rainbow sharks is greatly exaggerated.


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## Maryland Guppy (Dec 6, 2014)

I too have one of these red tailed sharks.
It is a one man cleanup crew, disturbs just enough substrate, and
cleans every plant in sight.
Watching him work glass on the front of the tank now.

Compatibility is no problem except for the black mollies.
It will provide a little chase at times, no harm done.
Once it realizes the molly is not one of it's own it's over.

Quite a character and seems way more intelligent than the live-bearers in my tank.
Will rest for several hours on the tips of it's fins on the bottom.
Unlike many fish upside down it is comfortable cleaning under ledges and large plant leaves.

Leaves all the fry alone as it swims through the brush.
Heck fry don't even run from it as they do run from the adult fish.

Own 1 or a dozen, two or three will harass each other terribly.
I believe they can grow to a 4 or 5 inch fish.
6 months here and from 1.5" to 3" in length.

Hope this helps and others have a good experience with this interesting fish.
I am unsure of their lifespan.


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## AquaHobbyist (Jun 8, 2016)

@bigbadjon and @Marylandguppy, thank you for your feedback! I'm glad to hear that your rainbow shark and red tailed shark are not aggressive, puts my doubts to rest. Really like the look of this fish, and would prefer not to have to return it to the LFS as he adds a bit more character to my tank. I'll continue to monitor the shark this week, but so far it looks like it will do alright in the tank. Thanks again for your feedback!


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## FreshwaterAdvice (Jun 15, 2016)

AquaHobbyist said:


> @bigbadjon and @Marylandguppy, thank you for your feedback! I'm glad to hear that your rainbow shark and red tailed shark are not aggressive, puts my doubts to rest. Really like the look of this fish, and would prefer not to have to return it to the LFS as he adds a bit more character to my tank. I'll continue to monitor the shark this week, but so far it looks like it will do alright in the tank. Thanks again for your feedback!


I would actually recommend returning them to your LFS. 

A red tail shark grows up to 7" long and a rainbow shark can also grow up to 5" long. Both of them are incredibly active fish species that need tanks of at least 48" long for the rainbow shark up towards 72" for the red tail shark. 

Your twenty gallon high tank is way to small for these fish and would not provide them with a comfortable environment.


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## bigbadjon (Aug 6, 2015)

You could keep either in a 20 gallon for quite awhile. 30 gallons is plenty for either fully grown. A red tailed shark is actually the smaller of the two and rarely exceeds 3 inches in an aquarium. A rainbow shark may get 6 inches but I doubt it.


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## Willcooper (May 31, 2015)

I had a red tail in a 125 long a few years back and it was only aggressive towards an albino rainbow shark I had. They eventually figured their sides and were fine. My initial though was your tank is too small long term but the previous poster seemed like they had more knowledge on the subject. Either way it was never aggressive towards other fish or inverts


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## ChristopherM (Mar 10, 2016)

https://en.wikipedia.org/wiki/Red-tailed_black_shark

"Size and age: Red-tailed black sharks can reach a length of 16 cm (6 in). They can live up to 8 years, although in some rare cases they have lived to be over 10 years old."

I had a Red-Tailed Black Shark when I was a kid. He was aggressive and I had to take him out of my tropical community tank and put him in a tank by himself. He lived for a year or so in his own tank and grew to between 4 and 5 inches long. When I was cleaning the tank one afternoon, I left the lid off as I had always done, for just about 1 minute as I stepped into the bathroom to dump out some water. I came back and he was dead on the floor. He had never jumped before and I never expected him to jump. I have never had one since.


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## AquaHobbyist (Jun 8, 2016)

Thanks for all the replies! 
@FreshwaterAdvice, @BIGbadJOHN, @Willcooper - Good to know that my red-tailed shark won't get much bigger than 3 inches though it looks like it's possible for it to reach 6 inches in some cases. 
@ChristopherM - So sorry to hear about your shark! I read that they are good jumpers, but I have my tank covered. 

Thank you all for your help!


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## AquaHobbyist (Jun 8, 2016)

Quick question: I'm planning on replacing my 6 danios with a small school of 6-8 rummy nose tetras. Will the red tail shark be compatible with rummy nose tetras or any tetras for that mattter? Thanks!


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## jrill (Nov 20, 2013)

I have always had red tail sharks in my tanks. Give or take 50 yrs of fish keeping. Some chase their tank mates and some don't. They can change disposition overnight though. Docile today, bully tomorrow. Most of my tanks have been 20 longs. 

Sent from my XT1585 using Tapatalk


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## AquaHobbyist (Jun 8, 2016)

Thanks @jrill for the info. So far the shark is docile, and hopefully will remain so....


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