The Basic Steps to Build a Working Aquarium

A Minecraft aquarium is a water-filled structure that holds fish and displays them in a contained space. The simplest version takes about 10 minutes to build: dig or construct a box at least 3 blocks wide and 3 blocks deep, fill it with water using a bucket or water source block, and place fish inside by catching them with a bucket. The fish will swim around and stay in the water as long as the container is sealed or deep enough that they cannot jump out.

To catch fish, craft a bucket (three iron ingots arranged in a V-shape on a crafting table), find a fish in any water source, and right-click it while holding the bucket. The fish will be trapped inside. Swim or walk to your aquarium and right-click the bucket against the water to release the fish. You can store up to one fish per bucket, so you will need multiple buckets if you want multiple fish.

The most common mistake is making the aquarium too shallow. Fish can jump out of water that is only 1 or 2 blocks deep, so aim for at least 3 blocks of depth. If you want an open-top aquarium, build the walls at least 3 blocks high so the fish cannot escape.

Key Takeaways

  • A basic aquarium is any water-filled container at least 3 blocks deep or 3 blocks tall, built from any solid block material.
  • Catch fish by crafting a bucket, right-clicking a fish in open water, then releasing it into your aquarium by right-clicking the bucket against the water.
  • Fish will not despawn or die in a properly sealed aquarium, so they stay indefinitely once placed.
  • Decorative aquariums look better with plants like seagrass and kelp, which you can place on the bottom or sides of the tank.
  • You can build aquariums in any biome, but tropical fish spawn only in warm ocean and lukewarm ocean biomes.

Choosing a Location and Container Shape

Pick a spot where you want the aquarium to be visible—near your base entrance, inside a building, or as a centerpiece in a room. The location does not affect how the fish behave, but it affects how much you will enjoy looking at it. Consider whether you want the aquarium against a wall (so you see it from one side) or in the middle of a space (so you can walk around it).

The container can be any shape: a straightforward rectangular box, a circular pool, an L-shaped tank, or even a large underground cavern. The only hard rule is that the water must be at least 3 blocks deep if the top is open, or at least 1 block deep if the top is sealed with a solid block. Most players build rectangular tanks because they are easiest to fill and decorate evenly.

For a 5×5×3 tank (width × length × depth), you will need 75 water blocks. You can fill it faster by placing a single water source block in one corner and letting it flow, or by using multiple buckets. Water will spread horizontally up to 8 blocks away from a source block, so a large tank may need water sources in multiple corners.

Filling the Aquarium with Water

The fastest way to fill an aquarium is to place a water source block in one corner and let it spread. Dig down to the bottom of your tank, place a bucket of water, and the water will flow outward and downward until it fills the entire space. This works best for rectangular tanks where the water can spread evenly.

If your tank is oddly shaped or has obstacles, you may need to place multiple water source blocks or use buckets to fill gaps. Water spreads 8 blocks horizontally from a source, so a tank wider than 8 blocks will need a source block somewhere in the middle. You can always place extra source blocks and remove them later once the tank is full.

Once the tank is full, check that the water is not flowing out through gaps in the walls. If it is, place solid blocks to seal the leak. If the top is open and you want to prevent fish from jumping out, place solid blocks or slabs around the rim, or build the walls 3 blocks high so the fish cannot reach the edge.

Catching and Placing Fish

Fish spawn naturally in water, but you can also catch them yourself. Craft a bucket by placing three iron ingots on a crafting table in a V-shape (one in the top-left, one in the top-middle, one in the middle-center). Find a fish in any ocean, river, or water source, hold the bucket, and right-click the fish. The fish will disappear and the bucket will show a fish icon.

Walk to your aquarium and right-click the bucket against the water surface or any water block inside the tank. The fish will be released and will start swimming. You can catch as many fish as you want, but you need one bucket per fish. Once a fish is in the aquarium, it will not despawn or die, so it will stay there indefinitely.

Different fish types spawn in different biomes. Tropical fish appear only in warm and lukewarm ocean biomes and come in many colors. Cod, salmon, and pufferfish spawn in cold and temperate oceans. Axolotls spawn in underground lush caves. If you want a specific type of fish, you may need to travel to the right biome to catch it.

Adding Plants and Decorations

Seagrass and kelp are the easiest plants to add. Seagrass grows on the bottom of the tank and looks like short green grass. Kelp grows upward from the bottom and can reach the surface. Both are found naturally in ocean biomes and can be broken and placed by hand. Plant them on the bottom or sides of your tank to make it look more natural.

You can also add coral blocks, which come in five colors: brain, bubble, fire, horn, and tube. Coral blocks must be placed in water and will die if the water is removed, so keep them submerged. Coral fans are smaller decorative versions that attach to solid blocks and look like real coral.

Sand, gravel, and dirt on the bottom of the tank make it look more like a real ocean or river. You can also add rocks, driftwood (made from dark oak logs), or custom structures made from stone or other blocks. Avoid placing torches or other light sources inside the water—they will not work underwater. If you want to light the tank, place light sources outside the glass or use glowstone and lanterns above the water.

Building a Glass Aquarium Wall

To see the fish clearly, build at least one wall out of glass. Glass is transparent and lets you watch the fish without them escaping. Place glass blocks in a frame around your tank, or build the entire tank from glass if you want a 360-degree view.

Glass is fragile and breaks easily, so be careful when building near it. You can also use tinted glass (made by combining glass with amethyst shards) to add color, or dark prismarine and prismarine bricks for an underwater aesthetic. Avoid placing glass on the bottom of the tank—use solid blocks instead so the water does not leak out.

If you want the aquarium to look polished, build a frame around the glass using wood, stone, or metal blocks. A 1-block-thick frame around the outside of the glass makes the whole structure look intentional and finished. You can paint the frame any color or style that matches your base.

Common Mistakes to Avoid

The most common mistake is making the aquarium too shallow. Fish can jump out of water that is only 1 or 2 blocks deep, so always build at least 3 blocks deep or 3 blocks tall. If your fish keep disappearing, depth is the first thing to check.

Another mistake is leaving gaps in the walls or floor. Water will leak out through any opening larger than a single block, and fish can escape through gaps. Seal all edges carefully, especially corners where two walls meet.

Do not place torches, lanterns, or other light sources inside the water—they will extinguish and will not light the tank. Place lights above the water or outside the glass instead. If you want underwater lighting, use glowstone, sea lanterns, or shriekers, which all work underwater.

Finally, do not forget that fish need water to survive. If you drain the tank or let the water dry up, the fish will die and disappear. Keep the tank full and sealed, and your fish will stay alive forever.

Frequently Asked Questions

Do fish need food in Minecraft?

No. Fish in Minecraft do not need to be fed. They will swim around indefinitely as long as they are in water. You do not need to do anything to keep them alive once they are in the aquarium.

Can I breed fish in an aquarium?

No. Fish cannot breed in Minecraft, even in large tanks. You can only have as many fish as you catch and place. Axolotls are the only aquatic mob that can breed, and they breed in water blocks at any depth.

What happens if I remove the water from the aquarium?

The fish will die and disappear within a few minutes. Always keep the tank full. If you need to drain it for repairs, catch the fish in buckets first and place them back once the tank is refilled.

Can I use a water bucket to fill a huge aquarium faster?

Yes, but it takes many buckets. A single water source block spreads 8 blocks horizontally, so for very large tanks, place multiple source blocks in different corners and let them spread toward each other. This is faster than filling with individual buckets.

Do I need to light the aquarium for fish to spawn?

No. Fish will spawn in dark water just as easily as in lit water. Light does not affect fish spawning or behavior. You can light the aquarium for decoration, but it is not necessary for the fish to survive.