Species

If your tap water is hard and alkaline, livebearers are the easiest win in the whole hobby. Hard water is not something they tolerate, it is what they evolved for, so the question is never whether a livebearer will cope. It is which one suits your tank. My tap runs at roughly 22 to 23 dGH with a pH around 7.2 to 7.4, which is very hard by any measure, and the livebearers in my tanks colour up and breed without me touching the water chemistry at all. That is the short version. The longer version depends on how big your tank is, how much breeding you can stomach, and how hardy you need the fish to be straight out of the bag. ...

If you keep a Tanganyikan tank on hard tap water and you want a catfish that actually belongs in it, Synodontis petricola is the one I reach for. It is a small, spotted, whiskery bottom-dweller from Lake Tanganyika, it stays sociable in a group, and it wants the same mineral-heavy, alkaline water that makes my shell-dwellers thrive. I have kept a little shoal of them under a colony of multies for years, and they are one of the least demanding fish in the house once you get two things right: the water and the diet. ...

If you have hard, alkaline tap water and you want a splash of solid yellow that is not a Malawi mbuna, the lemon cichlid is one of the best fish you can put in it. Neolamprologus leleupi is a small rock-dwelling cichlid from Lake Tanganyika, the colour of a ripe lemon from nose to tail, and it wants exactly the mineral-heavy water that comes out of my tap. I keep mine in a Tanganyikan tank alongside shell-dwellers, and once you understand its one real quirk, its temper with its own kind, it is a straightforward, long-lived fish. ...

If you have hard, alkaline tap water and want something with real presence that is not a Rift Lake cichlid, the paradise fish deserves a look. It thrives across a huge range of hardness, sits comfortably in water like my 22 to 23 °dGH tap, and it is one of the few genuinely tropical-looking fish you can keep in an unheated room. The catch, and there is always a catch, is temperament. A male paradise fish is a bold, territorial little fighter, so this is a fish you plan the tank around rather than dropping into an existing community. Get that one decision right and it is among the most rewarding and undemanding fish I have kept. ...

Tropheus are, on paper, the perfect fish for water like mine. They come from Lake Tanganyika, the hardest and most alkaline of the great Rift Lakes, so my 22 to 23 °dGH tap that soft-water fish hate is close to what they evolved in. They are stunning, they graze the rocks all day like little goats, and a settled colony in a big tank is one of the finest sights in the hobby. So why do I steer most people away from them? Because Tropheus punish two mistakes harder than almost any other cichlid: the wrong diet and the wrong group size. Get either wrong and you will not get a warning, you will get dead fish. ...

Gouramis are some of the most rewarding fish for a calm community tank, but the one everyone reaches for first, the dwarf gourami, is the one I most often talk people out of. On hard alkaline water like mine, at 22 to 23 °dGH, the choice of species matters twice over: once for how the fish handles the chemistry, and once for how likely it is to arrive already carrying something it will not recover from. Get the species right and gouramis are hardy, characterful and long-lived. Get it wrong and you are in for a slow, frustrating loss. ...

Yes, you can keep corydoras in hard water, but only some of them, and the honest picture is more nuanced than the forums usually let on. On my tap, which runs around 22 to 23 °dGH with a pH near 7.2, I have kept bronze and albino cories for years with no trouble at all. I have also watched more delicate wild-type species sulk and fade in the same water. The species you choose matters far more than any bottle of buffer you might be tempted to buy. ...

If I could only keep one invertebrate in a freshwater tank, it would be the Amano shrimp. They earn their place: a well-stocked group grazes hair algae and biofilm all day, they are tough enough to shrug off the sort of water that kills fussier shrimp, and my very hard tap water is closer to ideal for them than it is for most of the fish I keep. I have run Amanos in tanks reading about 22 dGH for years, alongside shell-dwellers and livebearers, and they have been some of the least demanding animals in the house. ...

If you want a shell-dwelling cichlid that does not spend its whole life picking fights, the caudopunk is the one I point people towards. Neolamprologus caudopunctatus (you will also see it written as Lamprologus caudopunctatus, and sold as the caudopunk) is a small Lake Tanganyika cichlid that hovers in the water like a little kite, breeds readily, and asks for nothing my hard tap water cannot already give it. It is calmer than a colony of multies and a good deal more forgiving than a bad-tempered Lamprologus ocellatus. If you are choosing a first Tanganyikan, this is a species I keep coming back to. ...

If you want one large, calm, genuinely impressive fish for hard alkaline water and you have the tank for it, the frontosa is hard to beat. Cyphotilapia frontosa is the humpheaded blue-and-white cichlid from the deep rocky slopes of Lake Tanganyika, and the water it evolved in is close to what comes out of my tap: hard, mineral-heavy and alkaline. That is the good news. The catch is size and patience. This is a fish that grows slowly, lives for well over a decade, and needs a tank most people underestimate. I keep a small colony, and the honest lesson from the first year was that I had bought a fish for the tank I wanted rather than the one I had. Let me save you that mistake. ...