Tank size · Freshwater
What size tank for a Koi angelfish (variant)? (55 gal minimum)
Koi angelfish (variant) (Pterophyllum scalare (koi variant)) — adult 6″, heavy-bodied, semi-aggressive.
The three sizes — minimum, good, ideal
| Tier | Tank size | What it gets you |
|---|---|---|
| Absolute minimum | 55 US gal | Survives adult life. No extras — no tankmates beyond the essentials, no aquascape that eats footprint. |
| Good | 83 US gal | Room for a small community, decor, and parameter buffering. This is where most people should aim. |
| Ideal | 138 US gal | Natural-feeling space. Active swimmers stop pacing, schoolers school freely, aggression drops. |
Length matters more than gallons here — a 30-gallon tall (24″ long) and a 30-gallon long (36″ long) hold the same water but support different fish. Koi angelfish (variant) needs at least 48″ of length.
Parameters at a glance
- Temperature
- 76–84 °F
- pH
- 6–7.5
- Adult size
- 6″
- Body type
- heavy
Why tank size matters for this species
Koi angelfish (variant) is an active swimmer. The 48″ minimum length is non-negotiable — they pace the front glass for hours in shorter tanks.
Source for the tank-size minimum
Angelfish Society USA.
Next steps
- ▸ Build a candidate stocking list with the aquarium stocking calculator — it'll warn if your community is incompatible.
- ▸ Confirm tank water volume after substrate and rock with the aquarium volume calculator.
- ▸ Read the nitrogen-cycle guide before adding the first fish.
People also ask
- What is the absolute minimum tank size for a Koi angelfish (variant)?
- 55 US gallons as an adult, with a minimum footprint of 48″ long. Angelfish Society USA.
- Can I keep a Koi angelfish (variant) in a smaller tank when it's a juvenile?
- Briefly, yes — fish stores often sell juveniles that haven't reached adult size yet. But you should plan, buy, and cycle the adult-minimum tank from day one. Upgrading mid-life stresses the fish and is far more expensive than buying the right tank up front.
- Can I keep more than one Koi angelfish (variant) together?
- It depends on the species' behaviour (semi-aggressive). Aggressive and semi-aggressive species often need to be kept solo unless the tank is dramatically larger than the minimum. Verify before adding a second.
- What temperature and pH does a Koi angelfish (variant) need?
- Temperature 76–84 °F, pH 6–7.5.
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