I read a lot of threads on many websites asking about suitable tankmates for bettas. I thought I'd do a write-up of some common species I hear as suggestions. These are just my experiences and research and people should feel free to comment and amend what I have written. :) Naturally, you should always take into account your individual betta's temperament.
THE GOOD: Snails
Snails are always a good starting point when figuring out if your betta is compatible with other species. If it attacks something as non-threatening as a snail, chances are it won't fare well with other species.
Snails are generally a safe bet, even if the betta objects at first. Their shells protect them from any initial nibbles, although some snails may lose their eyestalks to over-aggressive bettas. Some snails, like nerites, are good algae eaters. Others, like malaysian trumpet snails, are good at stirring up substrate, and assassin snails can be introduced to deal with infestations of other snails. That, of course, is one of the downsides – snails breed like crazy. They also have a high bioload for their size and are not a good idea in less than 5 gallons.
If you have a 15 gallon tank or larger, then a smaller species of pleco, like the bristlenose, may be an option. Although large fish, reaching 6 inches, they are generally peaceful and juveniles make short work of many types of algae. Adults would rather nom on food you supply, and plecos should have driftwood in their diet. Bettas are generally quite likely to accept these non-threatening bottom dwellers. The downside? Their huge bioload, and the fact that inexperienced petshop employees may well sell you a common pleco by mistake. Commons can get 2ft long.
These little catfish are favourites with many aquarists. They range in size from the tiny pygmies, perfect for a ten gallon, through the small, sensitive pandas up to the larger bronze and emerald species. They come in many attractive varieties.
Cories are great for cleaning up leftover food, but expect to have to supplement their diet with sinking meaty pellets. They are NOT algae eaters. They don’t eat poop, either. Again, as bottom dwellers, cories are a non-threatening species that most bettas should tolerate well.
Although shrimp may well become a snack for bettas, they are excellent tankmates. They have a miniscule bioload. They come in a variety of sizes – the algae eating amano shrimp, the scavenging ghost shrimp, and the attractive red cherry shrimp, who do a bit of both. You may not want to risk more expensive varieties, like crystal reds and tigers, with your bettas.
Shrimp will always stand a better chance of survival in a densely planted tank. Java moss is a really good, hardy plant that provides plenty of cover for them.
THE NOT BAD: Tetras
There are a lot of different species of tetra out there, some better than others. The species I always recommend are embers. They are very small, not as active as most tetras and not at all nippy – in short, perfect betta tankmates. They are not even remotely threatening and are very pretty. They are perfect for a ten gallon.
Other good tetras for a 15 gallon or larger include neons and variants like black neons; cardinals; glowlights; and pristellas. In a 20 gallon or up, you could potentially consider rummynoses, bloodfins, and head-and-taillights. Blind-cave tetras are an option, but may nip at first.
Avoid larger, more territorial tetras such as bleeding hearts, red-eyes, serpaes and black phantoms. Also avoid those with long fins, such as black widows, which may become a target for bettas.
In a 20 gallon tank, kuhli or Pakistani loaches are generally pretty good. The betta may be a bit baffled by these eel-things, but so will your visitors, because there is no denying that loaches are very cool. The massive, poop-machine, insanely-active clown loaches may not be a good idea, though.
Guppies can be a hit-and-miss idea. Males, with their long fins, may be very attractive to nippy bettas, and may nip in return. Duller males or females may be less of a problem, but their similar size may still make them enemies.
These tiny livebearers are less threatening, due to their small size, and still provide a nice splash of colour without sending bettas into murderous fits.
Like guppies, the larger size and bright colours of the platy may either stress or infuriate the betta, but with their shorter fins they are less likely to be targets of nipping.
Not generally a good idea. Mollies are big, can be nippy and generally do better in brackish water, which bettas can’t tolerate.
In a 20 gallon or larger this might work, but swordtails are big and colourful, and could easily freak your betta out.
Although peaceful cherry barbs may get on well with bettas (though watch out for male barbs harassing similar-coloured females when they want to mate), other barbs may not work out so well. Tiger barbs are notoriously nippy. Ruby, chilli and checked barbs are all possibilities. Keep them in large schools to avoid nipping problems.
Very cute, generally small and almost always peaceful. Keep your rasboras in a school of 6 or more and they shouldn’t bother your betta. Harlequins are the most common rasboras, but micro-rasboras such as borasas maculate and borasas brigittae are attractive, if sensitive, alternatives.
Like many species, a bit hit and miss. Like bettas, hatches love to jump, so a lid is needed. Hatchets are cool top-dwellers, but may be stressed out by a betta. Also, they look like a giant floating fin, just waiting to be nipped...
African Dwarf Frogs
Generally, ADFs are pretty good tankmates. There are a couple of risks, though – they don’t have the best eyesight and may well latch on to the betta’s tail by mistake. They are also slow to get food, meaning you may have to do some tedious spot-feeding.
There is such a massive assortment of killies, it’s just not possible to say outright yay or nay. Generally, though, given their bright colours, it’s a nay.
THE BAD: Danios
Although very hardy and attractive, there are several problems with danios (and their genetically altered cousins, glofish), as betta tankmates. They are very fast and active, which may stress the betta, are technically sub-tropical, liking cooler temperatures, and may be nippy.
Sticking two fish as territorial as a betta and a cichlid in a tank is generally asking for a disaster. I have seen this work in very rare and limited circumstances, most of which were just pure luck, but it’s really, really not a good idea. Cichlids include angelfish.
They are closely related to bettas and will fight.
Obviously, there are peaceful bettas like betta imbellis who will live together well, and sororities may well by very successful, but never put two male betta splendens together. Male and females should only be together in special circumstances, such as breeding.
These awesome crustaceans will snack on your betta’s fins, then his body. Same goes for crabs.
Not good for the same reason they shouldn’t be kept in community tanks: hugely aggressive, quite out of proportion with their tiny size. Many species are also brackish, frequently needing full saltwater as they age.
Too big and too aggressive.
Goldfish (and other coldwater fish like minnows)
They are coldwater. Bettas are tropical. Nuff said.
Too big. Waaay too big.
Sorry about how long this is. It's by no means an exhaustive list, just the species I could think of. :)
Much like plecos, otos are good little algae eaters, but stay small, maxing out at just 2 inches. However, they do prefer to be in schools, and their extreme sensitivity due to the methods used to catch them in the wild make a 20 gallon the minimum new oto-keepers should try them in. The water quality in smaller tanks is generally not stable enough. An acclimatised oto can be moved to a smaller tank later, provided it has other oto buddies.
As betta tankmates they are good, being inconspicuous, peaceful and good at swimming away. Just make sure you have plenty of algae for these voracious herbivores.
I'm just recently getting into this hobby (read: a month). We've got two bettas, one in his own 10 gallon tank and one in a community 29 gallon tank. Like you said, it seems that the Bettas temperament seems to be the primary driving force in most of these 'maybe yes-maybe no' fish.
I second platies, guppies etc. in the 'not bad' category. One of our Bettas, a small little guy, is a fierce warrior. He is constantly patrolling every inch of his tank, day/night it's insane. I worry he never rests. He is fun to watch though. Anyway, I knew he probably wasn't going to get along in the community tank, but I thought we'd try anyway, and see if maybe it would be OK. Well, it wasn't. He was crazy while floating in his cup, and when he finally calmed down, we let him out. He chased after a few guppies (non-flashy lyre-tails) and even black platies as fast as he could. Thankfully he couldn't catch them, but we took him out, disappointing, but unsurprised.
We put our other betta in there, one who I've seen flare his gills once or twice, and never his fins. He was a little on edge in the cup, and when we released him, he explored, chose a section, and started chasing fish away from it. A few days later, he didn't even pay any attention to the other fish, and didn't even care that they were hanging out in his little area of Val grass. It's been a great success so far.
So, on the one hand, guppies and platies were a no-no. But with the other betta, it was a piece of cake. Those middle fish definitely depend on the temperament of the betta, I think.
The glofish NEVER stop but the betta is very mellow. He will flare for food the 'look at me oh food giver' when ever he sees someone walk by the tank but he seems to leave the other fishes alone. He is a crowntail and I have seen NO damage to his fins from the glofish or the cories. The tank is fairly heavily planted so that may be helping by giving lots of places to hide.
I have 7 glofish in a 20L with my male crowntail, they get along fine
Hi there... Glofish aren't a problem on 'getting along'. If you researched your little Glo buddies you'd realize in fact they would be better housed with Goldfish because they cannot tolerate warmer temps over extended periods. I've found they prefer 74*, and being exposed to 80*-82* regularly will have them sick/lethargic. If yours are holding up, it still isn't ok. That's like those bettas in .5 gallon bowls with weekly water changes... are they alive and healthy? Yes. Is it cruel? Yes.
Seriously rethink your fish choices...
As for the guide, you did awesome! Everything seems to be right on the dot. Although, I think shrimps are technically considered 'ifs'. Other than that, it's perfect! It should be stickied to help newbies!
i had an ADF with Zen for a while.. they got along famously, until it came time for noms. Zen would try to bully Fribbit, Fribs would turn around and kick Zen full in the face. they held their own against each other (Zen's a big guy), but i did end up separating the two after a while