Angelfish Care Guide

The freshwater angelfish (Pterophyllum scalare) is a South American cichlid with a tall, disc-shaped body built for slipping between reeds and roots. Adults grow much bigger than the shop-sized juveniles, eat small fish, and are calm in a group until a pair forms. It suits a keeper with an established, cycled tropical tank of 100 cm (40 in) or more, rather than a first small aquarium.

Care requirements

Need	What to provide
Enclosure	Tank at least 100 cm (about 40 in) long, with tall plants or other vertical cover and a mature biological filter (FishBase; RSPCA)
Temperature	75–86°F (24–30°C), with a thermostatic heater and a daily thermometer check (FishBase; RSPCA)
Lighting	8–10 hours of aquarium light a day, off at night. Keep the tank away from windows (RSPCA)
Diet	Omnivore. Feed quality flake or pellet as the staple, plus frozen (thawed) daphnia, brine shrimp or bloodworm. Two or three small feeds a day, only what they eat in 2–5 minutes (National Aquarium; RSPCA)
Lifespan	Hobbyist guidance commonly cites around 10 years with good care
Social needs	Groups of 5 or more. Pairs that form become territorial at spawning time (FishBase)
Legal notes	No common restrictions; check local rules.

Sizing the tank: long and tall

FishBase gives a maximum length of 15 cm (6 in) and recommends a minimum tank length of 100 cm. The National Aquarium puts the maximum at 7 in (18 cm). Those figures are body length. Mature angelfish are often taller than they are long because of their long dorsal and anal fins, so tank height matters too. A standard 40 in (100 cm) tank of moderate height works better than a long, shallow one.

Stocking adds to the volume needed. The RSPCA’s rule for tropical fish is 1.5–2 litres of water per centimetre of fish body length, not counting the tail. A group of five angelfish with 10 cm (4 in) bodies already needs 75–100 litres (about 20–26 gal) under that guideline, before you add any tankmates. Treat this as a floor rather than a target. The RSPCA notes water quality also depends on filtration, temperature and how well you maintain the tank.

Water: warm, stable and cycled

Wild angelfish live in slow, densely vegetated swamps and flooded ground in the Amazon basin and other South American rivers (FishBase; National Aquarium). FishBase gives a pH range of 6.0–8.0 and hardness of 5–13 dH. Swings in temperature and pH cause more problems than the exact value.

Cycle the tank before adding fish. The RSPCA recommends fishless cycling for at least two weeks: keep testing until ammonia and nitrite spike and then return to zero. After that:

• change 10% of the water weekly with a siphon
• rinse filter media in the removed tank water, never under the tap
• test ammonia and nitrite every two weeks
• warm replacement water to tank temperature first, because a sudden drop shocks fish (RSPCA).

Tankmates and the pairing problem

In the wild, angelfish eat insects, worms, fish eggs, algae and fish fry (National Aquarium). In a tank, any fish small enough to fit in an adult’s mouth is potential food. Tiny tetras that look fine beside juvenile angelfish can disappear as the angelfish grow. Choose peaceful tankmates that will still be too large to swallow when the angelfish are fully grown. Avoid fin-nippers, which go for the angelfish’s long ventral fins.

Angelfish spawn on leaves, roots and flat surfaces, and both parents guard the eggs (National Aquarium). A bonded pair claims a spawning site and chases everything away from it. FishBase advises keeping breeding pairs in their own smaller tank. In a community tank, plan on removing a pair or rehoming the rest of the group if the chasing becomes constant.

Gotchas

• Buying for the shop size. Coin-sized juveniles grow to 6–7 in (15–18 cm) tall fish that need a tank 100 cm long (FishBase; National Aquarium).
• Neon-sized tankmates. Angelfish naturally eat small fish, so very small schooling fish become food as the angelfish grow (National Aquarium).
• A single angelfish or a group of two. FishBase recommends groups of five or more. In smaller numbers, one fish often takes the brunt of the aggression.
• Adding fish to an uncycled tank. Ammonia and nitrite spikes in a new tank can kill fish. The RSPCA advises at least two weeks of fishless cycling first.
• Overfeeding. Uneaten food rots and fouls the water. The RSPCA advises underfeeding rather than overfeeding, because fish cope better with less food than with poor water.

Avoid

• Unheated tanks, or heaters without a thermostat
• Untreated tap water: chlorine harms both fish and filter bacteria (RSPCA)
• Washing filter media under the tap, which kills the beneficial bacteria
• Holiday “feeding blocks”, which release a lot of food that rots (RSPCA)
• Fin-nipping tankmates, and fish small enough to be eaten
• Placing the tank by a window or radiator, where water can overheat (RSPCA)
• Cigarette smoke and aerosol sprays near an open-topped tank (RSPCA)

Signs to see a vet

The RSPCA suggests checking new fish for split fins, white spots, open sores or concave bellies. Watch for the same signs in your own tank, along with clamped fins, gasping at the surface, or a fish that hides and stops eating. Test ammonia and nitrite first, because poor water causes most of these. If the water is fine and the signs persist, contact a vet who treats fish.