The good, the bad and the ugly
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.
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:
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.