Animal section
Fish
Freshwater and tropical fishkeeping, water chemistry and stocking.
Species profiles
Standardised husbandry data for each animal in this group.
Betta (Siamese Fighting Fish)
Bettas are personable, intelligent fish that are routinely mis-sold as low-maintenance. A small heated, cycled and planted aquarium transforms their quality of life.
Lifespan 3–5 years · Care complexity 2/5
Goldfish
A well-kept goldfish is a long-lived, large and interactive pet, which is exactly why the traditional bowl fails them so badly.
Lifespan 10–25 years · Care complexity 3/5
Guppy
Guppies are colourful, hardy and prolific, making them an excellent introduction to keeping a balanced planted aquarium.
Lifespan 2–3 years · Care complexity 2/5
Freshwater Angelfish
Angelfish are elegant, deep-bodied cichlids that reward a tall, well-planted tank with striking display behaviour, but their territorial streak means tankmates need careful choosing.
Lifespan 10 years or more in well-kept tanks · Care complexity 3/5
Corydoras Catfish
Corydoras are gentle, sociable bottom-feeders that do best in same-species groups over soft sand. They are one of the easiest community fish to keep well.
Lifespan 5–10 years, sometimes longer · Care complexity 2/5
Discus
Discus are often called the king of the freshwater aquarium for their colour and shape, but they need pristine, warm, soft water maintained with real discipline. They suit experienced fishkeepers who enjoy a demanding, rewarding project rather than a first tank.
Lifespan 10–15 years · Care complexity 5/5
Neon Tetra
Neon tetras are the classic beginner shoaling fish, bringing constant movement and colour to a modest, well-cycled community tank. Their main risk is disease introduced with poor-quality stock rather than any husbandry difficulty of their own.
Lifespan 5–8 years with stable water quality · Care complexity 2/5
Harlequin Rasbora
Harlequin rasboras are hardy, peaceful shoaling fish that suit new fishkeepers wanting an active, colourful community tank without the fussiness of some tetra species.
Lifespan 5–8 years · Care complexity 2/5
Oscar
The oscar is a large, intelligent South American cichlid that recognises its keepers and can live over ten years. It needs a big, powerfully filtered aquarium and is not a community fish.
Lifespan 10–15 years · Care complexity 3/5
Bristlenose Pleco
The bristlenose pleco is a small, peaceful algae-grazing catfish that stays around 12–15 cm. It needs driftwood, vegetable foods and good filtration, making it a sensible pleco for most tanks.
Lifespan 5–10 years · Care complexity 2/5
Platy
The platy is a hardy, colourful livebearer and one of the easiest freshwater fish for beginners. It breeds readily, so plan for fry or keep a single-sex group.
Lifespan 3–5 years · Care complexity 1/5
Molly
The molly is a peaceful livebearer that thrives in hard, warm water and sometimes slightly brackish conditions. It needs more space and stable water quality than its beginner reputation suggests.
Lifespan 3–5 years · Care complexity 1/5
Cherry Shrimp
Cherry shrimp are small, bright red freshwater shrimp that clean algae and biofilm in planted tanks. They need a cycled, copper-free aquarium and stable water rather than much hands-on care.
Lifespan 1–2 years · Care complexity 2/5
Swordtail
The swordtail is an active, hardy livebearer named for the male's sword-shaped tail. It needs a longer tank with swimming space and a cover, as it can jump.
Lifespan 3–5 years · Care complexity 1/5
Koi
Koi are ornamental carp that can exceed 60 cm and live for decades. They need a large, deep, well-filtered pond rather than an aquarium, plus seasonal feeding adjustments.
Lifespan 25–35 years, occasionally over 50 · Care complexity 4/5
Guides for this group
Care, health, behaviour and nutrition reading.
AquaticsAquarium Water Chemistry and the Nitrogen Cycle
Most fish illness is a water quality problem. Understanding cycling is the core skill of fishkeeping.
Petarium Editorial · 3 min read · Updated 2026-10-19
Buying guidesChoosing Your First Aquarium Setup
What to buy, what to skip, and why the biggest tank you can fit is usually the easiest to keep.
Petarium Editorial · 3 min read · Updated 2026-10-07
Getting startedSetting Up a First Aquarium: A Month-by-Month Guide
Why the first fish should go in weeks after the tank, not days — and what to actually do while you wait.
Petarium Editorial · 3 min read · Updated 2026-10-07
AquaticsSetting Up a First Aquarium Without Losing Fish
The nitrogen cycle, why the first six weeks decide everything, and how to choose stocking that suits the tank rather than the shop display.
Petarium Editorial · 3 min read · Updated 2026-10-07
Welfare scienceAnimal Sentience: What Science Can — and Cannot — Tell Us
How researchers study pain, pleasure, preference and emotion across species, and where uncertainty remains.
Petarium Editorial · 3 min read · Updated 2026-10-07
Farmed animal livesFarmed Fish Welfare: The Overlooked Food-System Question
What fish may experience in aquaculture, from stocking and water quality to handling, transport and slaughter.
Petarium Editorial · 3 min read · Updated 2026-10-07