Aquarium reference
Glass, weight, stands, filtration and water chemistry: the reasoning behind the calculator.
Each article covers one model and its limits, so you can check whether the numbers apply to your tank. For your own dimensions, use the calculator.
Fish and invertebrates
Livebearers
MollyA livebearer that needs hard, alkaline water. In soft water it falls ill, and no amount of medicine makes up fGuppyGuppies forgive a beginner most mistakes, but not overfeeding and not cold water. A pair in 20 litres will surPlatyA peaceful livebearer that breeds without any help from its owner. A good first fish, provided the tap water iSwordtailA livebearer with a sword on its tail. Its temper depends on how many females share the tank and on whether thEndler's guppyA tiny livebearer from Venezuela that lives in a nano tank and breeds on its own. The hard part is not buying
Characins
Black skirt tetraA silver tetra with a black skirt and a calm temper. While the shoal is large it leaves its neighbours alone; Neon tetraA neon looks its best only in a school and in soft, slightly acidic water. In a new tank it dies from pH swingTetrasA genus of small characins, represented in tanks by the rosy tetra, H. amandae, the lemon tetra and the black
Barbs and danios
Tiger barbA shoaling barb with four stripes and a reputation for nipping fins. What a shoal needs in order to live long,ZebrafishA hardy shoaling fish that swims at the surface and rarely needs a heater. What to know before you buy one, anGloFishA fluorescent zebrafish carrying a jellyfish or coral gene. Care is the same as for a plain zebrafish, but bre
Cichlids
AngelfishAn angelfish grows larger than it looks in the shop and needs a tall tank. A pair in 100 litres will live a doGreen terrorThe green terror lives in cool water and needs a tank from 250 litres. Why it does not go into a community tanBlood parrot cichlidThe blood parrot was created by people and does not exist in the wild. It is hardy and peaceful, but its smallOscarAn oscar grows to 35 cm and lives up to 20 years, so it is worth buying only for a big tank. What it actually Cichlasoma cichlidsThe trade sells dozens of fish from different genera under the name cichlasoma. Here is what they have in commRam cichlidA small cichlid from the llanos of the Orinoco that wants warm, acidic water and a mature tank. What it eats, DiscusA calm Amazonian cichlid with a reputation for being difficult. It forgives little: it needs stable soft waterSeverumThe severum looks like a discus but is far easier to keep. It grows to 20 cm and lives more than 15 years, so Jewel cichlidA scarlet African cichlid with a hard temper. Care is simple, but tank mates are hard to pick: while spawning,KribensisA dwarf cichlid from West Africa that most people start their first spawning with. Care is simple, but the watBlue dolphin cichlidA large and surprisingly peaceful Malawi cichlid. It grows to 25 cm, so the tank has to be 300 l and up and at
Catfish
Bristlenose plecoA bristlenose pleco cleans the glass while young and needs driftwood for life. Tank size, temperature, feedingCorydorasA corydoras cleans the bottom but does not replace siphoning. A school of five catfish needs sand, cover and 5Sailfin plecoA sailfin pleco is sold as a 5 cm juvenile and grows to half a metre, living twenty years. What an adult needsHoplo catfishThe hoplo catfish breathes air, builds a bubble nest and forgives a beginner almost any mistake with water. WhSynodontis catfishThe upside-down catfish fits in sixty litres, the featherfin squeaker needs three times that. Which species to
Labyrinth fish
BettaOne male in a small tank lives longer and looks brighter than he does in a community aquarium, as long as you Three spot gouramiA large labyrinth fish that forgives mistakes with water but turns into a bully with age. It lives for years aDwarf gouramiA peaceful labyrinth fish for a planted tank of 50 litres or more. It often arrives from the shop already sickParadise fishThe first aquarium fish of Europe and one of the most quarrelsome. It takes cool water but needs a tank of its
Goldfish
GoldfishA round bowl kills a goldfish faster than any disease. It needs 100 litres or more, a powerful filter and coolTelescope goldfishA short-bodied goldfish with bulging eyes that needs a cool tank of 100 l or more and careful decor. Here is wVeiltail goldfishA goldfish whose tail is longer than its body, and which needs a roomy coldwater tank plus careful handling ofComet goldfishA fast long-bodied goldfish with a long tail, which needs open water and a lid over it. Here is the care, with
Other
Ocellaris clownfishThe marine fish made famous by Nemo, with its anemone partnership and its change of sex. What an 80 l tank hasLoachesSchooling bottom fish with a hierarchy and a habit of clicking. A clown loach outlives a dog, which is worth kPufferfishA puffer with a beak instead of teeth, which needs snails and a tank of its own. Why it is dangerous, and why Siamese algae eaterIt eats black brush algae, but only in a group and only while it is hungry. And it grows noticeably bigger thaLabeoA large bottom fish that grows into the owner of the tank. It lives for more than fifteen years, so the decisiRainbowfishSchooling fish from New Guinea whose colour depends on water and food. Shy, jumpy and always on the move.Kuhli loachA loach sold as a snake-like fish and then not seen for weeks. It needs sand, soft water, a tight lid and food
Shrimp
Amano shrimpAmano shrimp grazes hair algae and green film, but dies from remedies with copper in them. Here are the volumeCherry shrimpCherry shrimp forgives tap water and breeds without effort, but it lives about eighteen months and loses colouBamboo shrimpA filter shrimp catches food with its fans and starves without current. Here is the flow, the suspension, the
Snails
Mystery snailA mystery snail will not cut your plants, but it fouls the water badly and likes to climb out. Here are hardneRamshorn snailA ramshorn arrives with plants and breeds without a partner. Here is when it is useful, why it fills the tank Nerite snailA nerite cleans the glass and will not multiply in fresh water. Here are hardness, feeding and the reproductivAssassin snailHelena eats ramshorns but will not end a population spike. Here are feeding, hardness and tank mates for this
Crayfish
Equipment and chemistry
Aquarium glass thickness: where the mm come fromA 150 cm tank needs noticeably thicker glass than a 60 cm one at the same height. Here is what the safety factor actually covers.Aquarium weight and volume: what it really weighsA 300 litre tank is 300 litres on the outside only. Water, glass and substrate add up to a figure the stand has to carry.Aquarium stand: span, deflection, panel thicknessA stand carries weight, not an aquarium, and it works as a beam. Getting the span 200 mm wrong costs more than a millimetre of plywood.Aquarium filter: bio-load and media surface areaA filter does not clean water: it is a home for bacteria and a mechanical trap. Media surface and nitrogen matter, litres per hour do not.Water tests and fertilizers: N, P and CO₂Tests are not for a tidy report. They show what is missing and what is piling up, and then the ratios start to matter.
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