Tank Size Help - Rainbow Shark and Bichir


Hi, long time reader, first time poster here.

I have multiple questions. First, I have heard of people housing Sengal/Dinosaur Bichir and Rainbow Sharks together before, but does anyone have any experience with this? How do they get along? I know they're both pretty territorial, semi-agro/aggressive fish. Would they do okay together in a 75 or a 90 gallon tank?

I currently have a single Rainbow Shark in my 55 gallon community tank, along with a school of White Skirt Tetras, 3 Kuhli Loaches, an Oto, 1 Siamese & 1 Chinese algae eater, and 3 Cory Catfish. I like my bottom feeders, sorry. Lol. But I am looking to purchase a 2nd tank to kind of use as more of an aggressive tank, so my little bottom feeders can feel a little more at ease. My Rainbow Shark is kinda a bully, and likes to chase them out of all the hiding places. He's definitely shown everyone in the tank that he's the boss. Even the tetras he will occasionally chase If they get in between him and an algae eater he's scaring off.
So I need to move him out, but Big Ozzie has been here since I started the tank, and I want him to be comfortable too. But.. if I'm getting another big tank for him, I'd really like to add a bichir, I've been wanting one for a while, and I recently found out that my local Aquarium Supply store can get the Sengal Bichirs in. I just don't really have the space to go much larger than a 90 for my next tank. The actual dimensions would probably be the 48×18×24 if I had to go with the 90 to house both.

Sorry for the novel, any help/advice would be appreciated, I do really have my heart set on a Bichir, but I definitely understand that fish need their space sometimes, and I don't have much floor space to offer.


well, depends on the type of fish characteristics they have. Sengal/Dinosaur Bichir are generally more aggressive to there own species but if you don't have a big enough tank, then both of them will be aggressive towards each other.

I'd say that a 90 gallon is cuttin it real close, same with a hundred. you sound like you have a bit more of an aggressive rainbow shark but you can definitely try them out together in the 100 gallon. I've had a friend where this worked out. for me it did not.


Bichirs senegalus are fairly peaceful. Not actively territorial like a rainbow shark can be.

I had a rainbow shark and bichir in 200gal and they never interacted. My rainbow shark primarily chased siemese algae eaters out of his territory.

Just keep in mind with rainbow sharks increased tank size doesnt always reduce their aggression. they can sometimes target specific species. Normally i would say 90gal-100gal would be fine especially if you provide caves and break line of sight using plants/wood.

Bichir are not exactly fast moving.... The rainbow shark my give a chase if bichir enters cave however the bichir should easily find plenty of spots to chill in a 90/100gal thats away from the rainbow sharks cave.


Good to know, and yea, my rainbow shark does the same, but he's never hurt anyone. He's never even gone after any fish that met their untimely end. Aside from the chasing, he's a fairly chill dude. Plus, I'm pretty sure he's a bit overweight:p

So basically, as long as I break up the sight lines, and transfer over his favorite cave, he should be fine in a 90/100 with a Bichir? Out of curiosity how quickly did your Bichir grow? The ones I've been able to find are relatively small, maybe 3 inches. Once the tank is established do you think I should introduce the Bichir first, or the Rainbow shark? Also, did you have good experience with other tank mates with the two of them? And if so, what tank mates should I look into getting?


Sounds like it will work alright. Add the bichir first to get settled. Then the rainbow shark.

I owned a bichir over 10 years ago so don't exactly remeber growth rate.... I'd say within a year then get around 8"... Max size can vary. Mine was on the smaller side.

Most tank mates will suit bichir.... as long as it doesn't fit in its mouth when it's fully grown :)!

I would suggest a group of 6 Hoplo catfish with rainbow shark and bichir. Hoplo catfish are robust and very active and fearless. Eat from your hand no problem.

Larger schooling fish would work too. I kept Denison barbs (red-line torpedo barbs) with mine. Lovely fish.

1 Bichir senegalus, 1 Rainbow shark. 6 Hoplocatfish. 10 Denison barbs.
If you can push to 125gal that would be even better ;).

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