I have a Betta fish and he is my first fish ever. I was planing on putting more fish in his tank, but I know Betta fish are aggressive to other fish. When I did some research, however, I found out that you can place some fish with the Betta.

What is the best fish I can put with a betta?

My tank is 5.5 gallons (21 liters).

  • The "best" fish is opinion and not good for this format. Please see this post for more information on how to better reword your question.
    – Zaralynda
    Oct 26, 2017 at 13:18
  • I'd stick with a snail, and not add any swimming fish... Too small of a space, male bettas are territorial by nature
    – Christy B.
    Oct 26, 2017 at 23:19

4 Answers 4


There are a 2 main reasons why a betta can become aggressive to other fish:

  • Visual apperance
    In general, a betta will only be aggressive to other fish if he thinks they are 'competition'.
    This can happen if the other fish has some visual similarities with other male bettas. Most important is the fin size.
    So as long as the other species has short fins it should be ok.
    For example: male guppies have larger fins, so I do not recommend them. But I did have a betta together with some female guppies.

  • Territory
    Betta's can be territorial. They need some space they can call their own.
    A betta will swim through all layers of water (top, middle, bottom), but they will make their nest on the surface. If other fish come near, they will try to defend it.
    So for this reason it's best not to add other species that mostly swim in the top layer, or that will also create their nest on the surface (like other fish with a labyrinth organ, like gouramis).

    Personally, I've had a betta together with some tetra's (middle layer) and corrydoras (bottom) without any problems.

If you want to add female betta's, you should add at least 2 females. Betta's live in a harem with a male - female ration of 1:2 or 3.
But the territorial aspect is also important here. If the male has build a nest, and the females come too close, he can still become aggressive. So for smaller tanks, this is probably not a good idea anyway.

Also you have to be sure the females are actually female. A while ago one of my 'female' betta's turned out to be a short-finned male. and they indeed started fighting (the short finned won, the other died :( ).

Ofcourse, before adding other species you also have to check if things like temperature, ph, size, water current are similar to the requirements of a betta.

  • Also adding females to mate has to be done carefully, some males will still attack their mate, even right after the mating ritual. In places like Segrest Farms and 5D fisheries, the females are only kept in long enough for fertilization and then are removed
    – Christy B.
    Oct 26, 2017 at 23:16
  • True, but this is mostly related to the 'territory'. With a large tank it probably won't really be an issue. I'll add it to my answer.
    – Diether
    Nov 2, 2017 at 11:10

How large is your tank and how is it setup?

Betas are hardly ever aggressive with any other fish except Betas. Typically females can be kept together, but males should be kept separate. Personally, I've never had a problem keeping a single male and a or multiple females in the same tank, but I have heard of this not working for some, so it should be done with caution.

The biggest issue with betas is people often keep them in small containers or unfiltered bowls and tanks. Not getting into the discussion on whether this is humane long term, but most other fish cannot survive like this long term. Betas have a different respiratory system than normal fish, it's called a labyrinth organ, and it allows them to directly breath air. They are also able to handle temperature swings much better than most other tropical fish.

Anyway, if you can update and describe how your tank is setup, we can more appropriately answer the question with specifics.

  • 3
    In that case, I would stick to just the betta. It's too small to add other fish.
    – Diether
    Oct 25, 2017 at 7:52
  • I have to disagree that bettas "are hardly ever aggressive with other fish Except Bettas"... also the labyrinth organ makes it so they have to come to the top to get air, and allows them to live out if the water shortly as they would in the wild with low tides, in tidal waters like paddy fields, floodplains, and marshlands, but this doesn't have any effect on which fish you can and can't keep them with UNLESS you have little to no filtration water flow
    – Christy B.
    Oct 26, 2017 at 23:13
  • @Christy. The common way people keep betas is in small <5 gallon, unfiltered, unheated, bowls and containers. There's almost no other tropical fish that can live under those circumstances for extended periods of time, that was the basis of my compatibility. They otherwise make great tankmates in non-aggressive community tanks IMO. As far as aggression, I personally have only 1 time in more than 25 years seen a beta show aggression towards a non-beta fish, and it was a congo tetra which has some resemblance in shape. While anecdotal, I haven't heard of many instances of beta aggression.
    – Jestep
    Oct 31, 2017 at 19:06
  • I think our experiences differ, which is a fair expectation
    – Christy B.
    Nov 1, 2017 at 13:50

Betta fish are aggressive and will eat other fish - including even species classified as "semi-aggressive".

I have heard some say that Hypostomus plecostomus will do OK with Bettas, but when I attempted this, my Betta began attacking my H. plecostomus. These definitely will not mix well with goldfish, which do better in a slightly colder temperature of 68-75 °F (20-24 °C), whereas Bettas are a tropical fish preferring the 75-82 °F (24-28 °C) range.


Any fish that won't fit into his mouth, except another betta. Also, no fish that can put a betta in their mouth.

What is more, some fish, like barbs, may nip at a bettas' long fins. You should look at a pamphlet on fish keeping; or websites (e.g. Houston fish box). Learn things like temperature intervals between 60 and 90 °F (16 - 32 °C), pH between 6.5 and 7.5.

But since I have read a bettas' natural home is a water buffalo's hoof-print filled with rain water, they are not very demanding. They, like all fish, love mosquito larvae. And as I think for companion fishes, a betta would say black mollies; large, slow moving delicious babies.

  • 1
    There are many other things to consider then simply 'size'. E.g. appearance , temperature, water chemistry,...
    – Diether
    Oct 25, 2017 at 7:57
  • Are you suggesting that the OP should or shouldn't keep mollies? It's not quite clear to me.
    – Henders
    Oct 25, 2017 at 20:45
  • i think a betta would like mollies for companions so he could eat the babies, About any fish will eat any other fish he can swallow; Exception one - Pirana can take a bite out of any fish ( I would not watch if I fed him a live fish) , And exception two - Koi are very vegetarian , my Koi ( 2 feet long ) do not touch the giant danios ( 4 inch long) in the pond. Oct 26, 2017 at 22:13
  • The tank is 5.5 gallons so adding anything isn't really appropriate. Mollies can get to a couple of inches so are not a good suggestion in my opinion.
    – Henders
    Nov 2, 2017 at 12:03

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