What Size Aquarium Do You Need for Arowana Fish? What Equipment Is Required

Summary: Arowana fish need a minimum of 180 gallons for a single juvenile, 250 gallons for an adult, and 400+ gallons for a pair. The tank must be at least 8 feet long because adult arowanas grow to 24-36 inches and need horizontal swimming space. I've overseen three five-star hotel lobby aquariums in my career. The number one mistake I see is people buying a tall tank thinking it's "bigger." Arowanas need length, not height.

We were renovating the lobby of a five-star hotel in 2019.

The owner wanted a centerpiece. Something that would stop people in the elevator lobby. Something that said "luxury."

He wanted arowana.

I had to tell him: "That's going to cost more than you think. And the tank size is going to be bigger than you think."

This is the story of how we spec'd that tank. And what I learned about arowana aquariums along the way.

The Fish Size Nobody Asks About

Here's what every arowana website tells you: "Arowanas grow to 24-36 inches."

They don't tell you the full story.

A juvenile arowana is 6-8 inches when you buy it. Cute. Small. Looks like it fits in a 50-gallon tank.

In 18 months? It's 20 inches. In 3 years? It's 30 inches.

That's 2.5 feet of fish.

And arowanas don't swim up and down. They swim horizontally. They need length, not height.

The Tank Size Breakdown

Here's the math I use:

Juvenile arowana (6-12 inches):

Minimum tank: 180 gallons (72" × 24" × 24")
Why: juvenile still growing, needs room to move

Sub-adult arowana (12-24 inches):

Minimum tank: 250 gallons (84" × 28" × 28")
Why: fish is growing fast, needs horizontal space

Adult arowana (24-36 inches):

Minimum tank: 400 gallons (96" × 30" × 30")
Why: fish is fully grown, needs room to turn around

The key number is length . Not volume. Not height.

An arowana needs at least 2x its body length in tank length. So a 30-inch fish needs a 60+ inch tank minimum.

We went with 96 inches. That's 8 feet. It gave the fish room to turn around comfortably.

The Building Problem

Here's the part nobody thinks about.

You can't just put a 400-gallon tank anywhere.

400 gallons of water weighs about 3,400 pounds. Add the tank, the stand, the rockwork? Another 800 pounds.

Total: 4,200 pounds.

That's 2.1 tons.

Most hotel lobbies aren't designed to hold that. We had to do a structural analysis. We had to reinforce the floor. We had to make sure the weight distribution was correct.

That added $15,000 to the project.

The owner didn't expect that. Nobody expects that.

The Equipment BOM

Here's what we specified for that 400-gallon arowana tank:

Filtration:

Two canister filters, rated for 200 gallons each
Total filtration: 400 gallons (1x tank volume, but redundant)
Why redundant: if one filter fails, the other keeps the tank running

Heating:

Two 500W heaters
Redundancy again. If one fails, the other keeps the tank warm.

Lighting:

LED lights, 6500K
Arowanas are top-water fish. They don't need fancy reef lighting.
Just enough light to show off the fish's colors.

Cover:

Glass lid with feeding hole
Arowanas jump. If they see something they want, they'll leap out.
We learned that the hard way on a previous project.

Water circulation:

Two powerheads, 2000 GPH each
Arowanas like strong current. It keeps them healthy. It also keeps waste moving to the filter.

The Cost Breakdown

Here's what that project cost:

Tank (400 gallons, 19mm glass): $8,500
Stand (custom steel frame): $3,200
Filtration (2x canister): $1,800
Heating (2x 500W): $400
Lighting (LED): $600
Structural reinforcement: $15,000
Installation and plumbing: $4,000

Total: $33,500

That's the cost of a proper arowana tank. Not the $2,000 "starter kit" you see online.

Those starter kits are for juveniles. The fish outgrows them in 18 months. Then you're back to square one.

The Mistakes I've Seen

In my career, I've overseen three hotel lobby aquariums. I've seen every mistake.

Mistake 1: Buying a tall tank. Arowanas need length, not height. A 4-foot-tall tank is useless for an arowana. It needs to be 8 feet long.

Mistake 2: Undersized filtration. Arowanas are messy. They eat a lot. They poop a lot. You need over-sized filtration.

Mistake 3: No cover. Arowanas jump. They will jump out. We lost one on a previous project. It didn't survive.

Mistake 4: No structural support. You can't put 4,200 pounds on a regular floor. It will crack. It will leak.

What I'm Not Going to Tell You

I can tell you what size tank to build. I can tell you what equipment to spec. I can tell you what the project will cost.

But I'm not going to tell you which arowana is the "best." I'm not going to tell you how to breed them. I'm not going to tell you how to get the perfect color.

That's not my department. I'm the engineer. I build the tank. I make sure it doesn't leak. I make sure the floor doesn't crack. The fish care? That's the customer's job.

What We Spec at Ruibit

When we build a custom aquarium at Ruibit, we don't just sell a glass box.

We start with the fish. We calculate the adult size. We spec the tank dimensions. We do the structural analysis. We build the BOM. We verify everything before production.

We also tell every customer: "This is not a $2,000 project. This is a $30,000 project. Budget accordingly."

That's what we've learned from years of commercial projects. The customers who budget correctly? They get a tank that lasts 10 years. The customers who try to save money? They come back 2 years later wanting to rebuild.