Fish you shouldn’t keep together

Fish you shouldn’t keep together

A fish tank is an exciting and beautiful addition to any house – it’s a combination of pets and, in a way, living art. But first time fish owners often get so wrapped up in buying cool tank accessories and loading up on the prettiest fish, that they don’t take the time to research what fish breeds are compatible – and which should definitely be kept apart! 

Ultimately, if you’re not sure you should ask at the shop – a good fish store owner should be fully clued up on which species can and can’t coexist, so follow their advice. Sadly, there are some store owners that just want to make a quick buck and will give you misinformation just to get you to go home with more purchases – and you wind up waking up the next morning not to find a serene scene from Finding Nemo, but something closer to Jaws. The Revenge. 

First, let’s start with what species are perfectly happy to live together in harmony – hence are very popular aquarium fish. Guppies, danios, angelfish and tetra fish are the perfect roomies. They have vibrant lovely colours, so they’re sure to make your aquarium a lovely scene, but they’re also pretty passive and peaceful breeds so they shouldn’t cause any problems. 

So why do fish fight in the first place? Well, it’s not because they’re hungry (or let’s hope not!) From your perspective, an aquarium is a relatively small container that serves as a pet enclosure – but for the fish, it’s their entire world. They will establish an ecosystem in your tank no different than they would in their natural habitat, so they will exhibit the same behaviours they would in the wild. Fish get territorial, so they will lash out if other species encroach on an area they’ve claimed as their own. They also get pretty frisky during mating season, especially if there aren’t a lot of females to go around. 

The best things you can do is to ensure that your fish have a big enough social group of their own species – including females. Yes, they tend to be less brightly coloured and fun to look at, but believe that they will help keep the males happier. You can rearrange your aquarium when you introduce new fish to the tank – existing fish will be fooled into thinking they’re in new territory, and it can help establish new boundaries. For the more timid fish, make sure you have plenty of hiding spots – this is where you can invest in cute little caves and other tank accessories that are fun for your setting and safe for your little buddies! In drastic cases, you can get special netting that you can use to separate the breeds that just won’t get along. And of course – don’t overpopulate your tank – fish need a lot of room to be comfy in, so don’t get overzealous with new purchases! Or, invest in a bigger tank.

Sadly, some species are just fundamentally aggressive. We’ve outlined some of the most common culprits below, so if you really want to keep these fish, either get a separate tank for them or only buy these particular breeds.

Betta Fish. There’s a reason their other nickname is the fighter fish – these guys are bullies, especially to the sweet little tetras. They’re a popular choice because their fins are arguably the most beautiful, but boy are they mean. Alas, even to each other. It’s best to keep no more than 2 or 3 in and in a very large tank so they can keep their distance.

Tiger Barbs. These stripy little guys are pretty cute, but they really don’t play well with others and have a tendency to target fish with longer tentacles that they can take easy bites out of. They’re happiest if they’re part of a large school of barbs, so if you do decide to include them in your aquarium, get at least 5 or 6. If you get one or two, they’re far more likely to lash out.

Red tail or Rainbow sharks. Poor sharks, they always get a bad rap don’t they. These small freshwater sharks like to explore every nook and cranny of the bottom of the tank, and get quite protective over it, so they’re more likely to have altercations with any lower dwelling species. In theory, they won’t lash out unless provoked, so they can be ok with barbs of danios that will just leave them to their own devices – but again, plenty of room will be required! Red tails are actually quite rare to find these days, as they are becoming more and more endangered in the wild. There are lots of other freshwater shark species suitable for aquarium living, but they do require quite precise care.

Dwarf Pea Puffer. These guys are often picked because they look quite cute, with their round bellies and big eyes, but they certainly don’t shy away from a fight. They’re best kept with their own species and most importantly – kept occupied. Their natural habitat is very busy and jam packed with natural life, so you need to try and recreate that environment. Get lots of plants, driftwood and tank decor so these guys have plenty of places to explore – and keep them away from the others!

Whatever breeds you decide to go for, make sure that you thoroughly read up on their care and optimal environment, in terms of light, temperature and feeding frequency. With a big enough tank and the right decor, you should have yourself a lovely little mini-reef. But if you’re a first time aquarium owner and a bit nervous about which fish are right for you, then you really can’t go wrong with a trusty goldfish! There’s beauty in simplicity and they can live for a very long time, so they’ll be good, hassle-free company for years. 


That’s me, the one writing this. Because Blue can’t type, it’s my job to do that. I’m a blogger in the UK with a passion for the planet, including everyone and everything on it! I’ve been a vegetarian since I turned 10, making that 30+ years of being meat-free. Reason – because I can’t bring myself to eat animals. I turned plant-based a couple of years ago and I am loving it.

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