Compare their water ranges
Freshwater angelfish: 24–30°C, pH 6–7.5. Fancy goldfish: 18–24°C, pH 6.5–8.5. A shared number is only a starting point; stable conditions and provenance still matter.
Plan for adult size and space
Use at least the larger baseline of 150 litres and 100 cm swimming length, then add margin for both animals’ full social groups, territory and waste.
Behaviour can override the numbers
Freshwater angelfish is described here as semi-aggressive; Fancy goldfish as social. Introductions need observation and a ready separation plan. This assessment is not a guarantee of individual behaviour.