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The honest answer to how long your aquarium light should be on is shorter than most people expect: six to eight hours a day for the great majority of tanks, set on a timer, and left alone. Longer does not make fish healthier or colours richer. What it mostly makes is algae. I learned that the hard way in my first year, running a light for ten hours because it looked nice in the evenings, then wondering why the glass went green every week. ...

The first time a batch of shell-dweller fry appeared over the sand in one of my tanks, I did what a lot of people do and reached for crushed flake. The fry ate it and survived. Then I tried baby brine shrimp on the next brood, and the difference was obvious within a week: fatter little bodies, faster growth, and far fewer that simply faded away. Baby brine shrimp, or newly hatched Artemia, is the single most useful thing I have added to raising fry, and hatching your own is cheaper and easier than it looks. ...

Few things worry a new fishkeeper more than watching a fish that cannot stay level. It bobs up to the surface and cannot swim down, or it lies on its side on the substrate, or it swims nose-down in slow circles. Nine times out of ten what you are looking at is a swim bladder problem, and the good news is that the most common cause is something you can fix at home and, better still, prevent. I have watched a fair few of my own fish go through this, mostly greedy livebearers that ate too much, and the pattern is usually the same. ...

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 your tap water is hard, you will meet limescale sooner or later. It shows up as a chalky white line where the water sits, a foggy film on the lid, and a crust creeping up the heater and the filter outlet. The first thing worth saying is that it will not hurt your fish. Limescale is a cosmetic nuisance, not a health problem, and once you understand what it is you can stop panicking about it and start managing it. I keep tanks on tap water that runs about 22 dGH, so I have scraped a fair amount of the stuff off glass over the years, and it turns out to be one of the easier problems in the hobby to live with. ...

Walk into the cichlid section of any shop and you will find a shelf of tubs promising to turn your tap water into Lake Tanganyika or Lake Malawi. Buffers, cichlid salts, trace element blends. The useful thing to say first is this: if your tap water is genuinely hard and alkaline, you almost certainly do not need any of them. I keep Tanganyikan shell-dwellers on tap water that runs about 22 dGH, and I have never once reached for a tub of buffer. My fish breed, colour up and get old. The shelf is aimed at people whose water is soft, and if that is not you, you are being sold a fix for a problem you do not have. ...

Every few weeks someone tells me their tap water reads pH 8, they have panicked, and they are halfway through emptying a bottle of pH-down into the tank. So let me say the useful thing first: a high pH, on its own, is almost never the problem people think it is. A stable pH of 8 will keep a great many fish in fine health for years. What actually harms fish is a pH that lurches up and down, and chasing a high reading lower is one of the surest ways to cause exactly that lurch. I keep tanks on tap water that runs about 22 dGH and sits firmly on the alkaline side, and I stopped fighting it a long time ago. ...

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 have hard, alkaline tap water and you want a tank that is loud with colour and constant activity, mbuna are one of the best things you can do with it. These are the rock-dwelling cichlids of Lake Malawi, small by cichlid standards but packed with personality and attitude, and the water they need is the water plenty of us spend money trying to get rid of. My tap runs around 22 dGH and buffers alkaline, and for a Malawi tank that is a head start most keepers would envy. This guide is how I set one up, and where the honest snags are, because a mbuna tank is brilliant fun but it is not a peaceful community and it is not forgiving of a soft-water mindset. ...

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. ...