Free aquarium planner

Tank Builder

Pick your tank size, add fish, and instantly see if they get along, how full the tank is, and the heater and filter you need.

Your fish will swim here

No size yet

1. Tank size

gal

2. Add fish

Start with the fish you want most

Search above or tap the box for popular picks. Schooling fish come in at their minimum group size.

Your build is kept on this device. Sign in to save it, add photos, share it on your profile and track water tests.

Add fish to get your score

Compatibility, stocking level, heater and filter sizes, and the water each fish likes all show up here as you build.

How the Tank Builder works

Set your tank size

Type gallons or litres, tap a common size, or measure your tank and we'll work out the volume.

Add your fish

Search 256 fish, shrimp and snails. Schooling fish come in at their minimum group size, and the tank picture shows where each one swims.

Read the results

You get a compatibility score, every problem explained in plain English, how full the tank is, heater and filter sizes, and tankmates that would fit.

Heater and filter size by tank size

Quick answers for the most common tanks. Tap a size for stocking ideas that pass our compatibility check.

Tank	Size (in)	Heater	Filter flow	Filled weight
5 gallon	16 × 8 × 10	15-25 W	20-30 GPH	~50 lb
10 gallon	20 × 10 × 12	30-50 W	40-60 GPH	~100 lb
15 gallon	24 × 12 × 12	45-75 W	60-90 GPH	~150 lb
20 gallon	24 × 12 × 16	60-100 W	80-120 GPH	~200 lb
29 gallon	30 × 12 × 18	85-145 W	116-174 GPH	~290 lb
40 gallon	36 × 18 × 16	120-200 W	160-240 GPH	~400 lb
55 gallon	48 × 13 × 21	165-275 W	220-330 GPH	~550 lb
75 gallon	48 × 18 × 21	225-375 W	300-450 GPH	~750 lb
90 gallon	48 × 18 × 24	270-450 W	360-540 GPH	~900 lb
125 gallon	72 × 18 × 21	375-625 W	500-750 GPH	~1,250 lb
150 gallon	72 × 18 × 28	450-750 W	600-900 GPH	~1,500 lb
180 gallon	72 × 24 × 25	540-900 W	720-1080 GPH	~1,800 lb

Aquarium FAQ

How many fish can I put in my aquarium?

It depends on how big the fish get and how much waste they make, not just their count. The Tank Builder adds up each fish's adult size, weights messy fish like goldfish, plecos and cichlids more heavily and shrimp and snails less, and compares that with a cautious limit for your tank. Under 90% is comfortable. 90 to 130% can work with strong filtration and regular water changes. Over 130% is overstocked.

How do I know if two fish are compatible?

Check five things: they need the same kind of water (freshwater, brackish or saltwater), their temperature ranges must overlap, neither should be big enough to eat the other, their temperaments should match, and schooling fish need their minimum group. The Tank Builder checks all of these at once and names the fish causing each problem.

What size heater does my aquarium need?

Plan on 3 to 5 watts per gallon. Use the higher end if your room gets cold or the tank sits near a window or outside wall. For tanks of 75 gallons and up, two smaller heaters at opposite ends heat more evenly and keep the tank safe if one fails. Coldwater fish like goldfish usually don't need one.

How big a filter do I need?

Look for a filter that moves 4 to 6 times the tank's volume every hour. A 29 gallon tank wants roughly 120 to 175 gallons per hour (GPH). For messy fish or a heavily stocked tank, aim for 8 times or more.

How do I work out how many gallons my tank holds?

Multiply the inside length, width and water height in inches, then divide by 231. A 30 × 12 × 18 inch tank holds about 28 gallons of water. In metric, multiply centimetres and divide by 1,000 to get litres. Tap “Measure it” in the Tank Builder to do the maths for you.

What temperature should I set my heater to?

Set it to the middle of the range all your fish share. The Tank Builder shows each fish's comfortable range on one chart, highlights the overlap, and gives you a heater setting.

Is the Tank Builder free?

Yes. It works without an account and remembers your build on your device. Sign in to save up to four tanks, add photos, show them on your profile, and log water tests over time.

How the Tank Builder works

Set your tank size

Type gallons or litres, tap a common size, or measure your tank and we'll work out the volume.

Add your fish

Search 256 fish, shrimp and snails. Schooling fish come in at their minimum group size, and the tank picture shows where each one swims.

Read the results

You get a compatibility score, every problem explained in plain English, how full the tank is, heater and filter sizes, and tankmates that would fit.

Heater and filter size by tank size

Quick answers for the most common tanks. Tap a size for stocking ideas that pass our compatibility check.

Tank	Size (in)	Heater	Filter flow	Filled weight
5 gallon	16 × 8 × 10	15-25 W	20-30 GPH	~50 lb
10 gallon	20 × 10 × 12	30-50 W	40-60 GPH	~100 lb
15 gallon	24 × 12 × 12	45-75 W	60-90 GPH	~150 lb
20 gallon	24 × 12 × 16	60-100 W	80-120 GPH	~200 lb
29 gallon	30 × 12 × 18	85-145 W	116-174 GPH	~290 lb
40 gallon	36 × 18 × 16	120-200 W	160-240 GPH	~400 lb
55 gallon	48 × 13 × 21	165-275 W	220-330 GPH	~550 lb
75 gallon	48 × 18 × 21	225-375 W	300-450 GPH	~750 lb
90 gallon	48 × 18 × 24	270-450 W	360-540 GPH	~900 lb
125 gallon	72 × 18 × 21	375-625 W	500-750 GPH	~1,250 lb
150 gallon	72 × 18 × 28	450-750 W	600-900 GPH	~1,500 lb
180 gallon	72 × 24 × 25	540-900 W	720-1080 GPH	~1,800 lb

Aquarium FAQ

How many fish can I put in my aquarium?

How do I know if two fish are compatible?

What size heater does my aquarium need?

How big a filter do I need?

How do I work out how many gallons my tank holds?

What temperature should I set my heater to?

Set it to the middle of the range all your fish share. The Tank Builder shows each fish's comfortable range on one chart, highlights the overlap, and gives you a heater setting.

Is the Tank Builder free?

Yes. It works without an account and remembers your build on your device. Sign in to save up to four tanks, add photos, show them on your profile, and log water tests over time.

Tank Builder

1. Tank size

2. Add fish

How the Tank Builder works

Set your tank size

Add your fish

Read the results

Heater and filter size by tank size

Aquarium FAQ

How many fish can I put in my aquarium?

How do I know if two fish are compatible?

What size heater does my aquarium need?

How big a filter do I need?

How do I work out how many gallons my tank holds?

What temperature should I set my heater to?

Is the Tank Builder free?

Keep going

Tank Builder

1. Tank size

2. Add fish

How the Tank Builder works

Set your tank size

Add your fish

Read the results

Heater and filter size by tank size

Aquarium FAQ

How many fish can I put in my aquarium?

How do I know if two fish are compatible?

What size heater does my aquarium need?

How big a filter do I need?

How do I work out how many gallons my tank holds?

What temperature should I set my heater to?

Is the Tank Builder free?

Keep going