Daily Question: Would Cory’s, betta’s and guppy’s be well suited in the same tank?

Danielle asks

Would Cory’s, betta’s and guppy’s be well suited in the same tank? From my research I believe they would but I understand google doesn’t always give the best advice.

In this case, you’ve been given bad advice.

All three are seen as community fish, but three different communities. In the wild Bettas, assuming you mean Betta splendens, are from tropical parts of Asia, they thrive in dark peaty waters, often in the shallows of rivers, or marshy areas where the flow is low. Thousands of years of selective breeding have hones firstly the aggression, for fighting matches, and lately, those long flowing fins that make them so recognisable.

Bettas thrive in tanks with low KH, GH, and pH, consider adding botanicals such as Indian Almond Leaves, low flow, and plenty of plants to give them somewhere to rest close to the surface. Don’t forget they need a tight-fitting lid, and a gap between the water surface and the bottom of the lid so there is an air gap for them to breathe.

Corys are from South America, and what they thrive in depends on which of the 467 species you are talking about. But in general, they like pH below 7 and KH and GH in the soft or medium-soft range. They need to be kept in groups and need a decent-sized tank with plenty of chances to snuffle around a sandy base. Whilst they can be compatible with Bettas make sure that the tank size is large enough for the Corys, but not too deep or with too high a flow for the Betta.

Guppies are where the problems truly start. Originally from South and Central America, and the Caribbean, the guppy needs hard water to thrive. Without the modifications of soft water fish they struggle to obtain enough calcium if kept in soft water, leading to gradual wasting of the bones, and the characteristic shimmies as the low calcium levels lead their nerve cells unable to send messages properly. Having evolved to live fast and die young in the wild they will still produce fry and males will still be harassing females right up to the point their bodies shut down and they spiral to the bottom of the tank.

Male guppies with their long flowing tails are like a red rag to a bull for Bettas, an aggressive male may well just spend the first few weeks hunting the guppies down and killing them one by one. A laid-back male may well have his fins nipped and shredded by the guppies, who, somehow, evolved a ‘defence’ of swimming straight up to a potential predator head-on. No one said guppies are particularly smart, they just reproduce on a level that would impress rabbits.

Instead of those three consider these instead.

If you have soft water and your heart is set on the betta, look for one that has small enough fins and can swim well and look at Pygmy Cory, I’d still advise a tank of at least 120 litres as the Pygmy Cory are wonderfully active fish, and spend more time in the plants than the floor. Heavily plant the tank and either use epiphytes or have half sand and half plant substrate.

If it’s the corys you like and your water is soft then what about a shoal of corys and a pair of apistogramma, again this is all dependent on your tank size, but there are hundreds of combos to choose from there. Without the Betta and the oh-too-tempting finage you can look at adding some tetras or similar. Stick to South America and you still have hundreds of options. Coral red pencil fish would be one I’d consider, just make sure they’re large enough not to get eaten when you buy them, avoid neon tetras, but cardinals are a staple for a reason, I love diamond tetras, and right now I have a tank of black phantom tetras in my eyeline, with the males displaying to each other, and the babies that have hatched in the tank flitting around in the leaf litter.

If you have hard water do not despair, have you looked at Paradise fish? I will point out that these are as, or more aggressive than Bettas, but give them enough space and plants to break their line of sight and they will lay off anything not the same shape and size. Add some White Cloud Mountain Minnows and consider turning off your heater and maintaining the tank as a temperate tank.

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Ruth McDonald

Sailed twice around the world, started my acedemic career as an archaeologist and somehow ended up lecturing on science and researching fish.

Tropical Fish Keeping UK