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Problems · Care basics

How to set up a fish tank layout: plants, hiding places and swimming space

Not urgent

How you arrange the inside of your tank matters to your fish, not just to you. Fish in a bare tank, with nowhere to hide, are often nervous and pale. Fish in a tank packed solid with decorations have nowhere to swim. A good layout has both: hiding places for shy and resting fish, and open water for active swimmers.

This guide covers caves, wood, rock and plants, where to put them, and how to leave space for swimming, cleaning and water flow. It's an aquascape, but you don't need to be an artist. You just need to think about what your fish do all day.

How to check it

Look at your tank from the front, the sides and the top, then watch your fish for a few days.

  • Hiding places: can every shy fish get out of sight? Does every cave-dwelling fish (plecos, many cichlids, some loaches) have a cave of its own?
  • Open water: is there a clear lane along the front or middle where a school of tetras, rasboras or danios can swim end to end?
  • Sight lines: can one fish see the whole tank from one spot? If so, a bully can watch and chase everyone from there.
  • Behaviour: are fish out and about with good colour, or hiding all day? Is one fish guarding a big area and chasing the rest?
  • Access: can you reach the glass to clean it, and vacuum the substrate? Does water flow reach every part of the tank, or are there dead spots where waste builds up?

When it's a problem

  • Normal: fish rest in cover but come out to feed and swim. Shy fish hide more for the first week or two in a new tank.
  • Too bare: fish hide behind the heater or filter, stay pale, dart around in panic, or pace the glass (see glass surfing).
  • Too crowded with decor: active schooling fish can't swim properly, food and waste get trapped behind rocks, and you can't clean.
  • Serious: one fish keeps chasing or nipping others, fish have torn fins, or a fish is stuck in a gap. Fighting is covered in aggressive fish. Unstable rock piles can fall and crush fish or crack the glass.

What to do right now

  1. Check rock piles are stable. Push gently. Anything that wobbles should be rebuilt with the base rocks on the tank floor, not on top of the sand.
  2. Add quick cover if fish are hiding behind equipment: a cave, a piece of wood or a clump of plants in a back corner.
  3. Break up sight lines if fish are fighting. Moving a few rocks, wood or plants into the middle of the tank creates separate areas. Rearranging the whole layout can also reset territories, so a bully has to start again.
  4. Remove anything sharp that is tearing fins.
  5. Take out rotting plants and leftover food trapped behind decor.

What to do next

Hiding places: caves, wood and rock

  • Caves: cave-dwelling fish want a snug cave. For zebra plecos, Seriously Fish suggests caves with an entrance only a little wider than the fish. Give one cave per fish, plus a spare or two, so nobody has to fight for one.
  • Wood: driftwood makes shelter, shade and, for some plecos, food. New wood often grows a white fuzz for a few weeks; see mold on driftwood. It can also tint the water brown; see tannins.
  • Rock: make sure any rock is safe for your water before it goes in. Some rocks raise pH and hardness. See rocks safe for aquarium use.
  • Shade: many fish feel safer in dim spots. Seriously Fish recommends arranging wood to make caves and shaded areas for rams, for example.

Open swimming space

  • Leave an open lane. Put tall decor and plants at the back and sides, and keep the front and middle more open. Active schooling fish use the whole length of the tank.
  • Length matters for swimmers. Seriously Fish suggests a base of at least 90 by 30 cm even for a small group of zebra danios, because they are so active.
  • Bigger is better. The RSPCA advises giving more than the minimum space, and choosing a wide tank over a tall one. A study of bettas (Oldfield and Murphy, 2024) found that fish in tiny bowls swam much less than fish in tanks of 10 litres or more.

Territories and sight lines

  • Make separate areas. Territorial fish, such as many cichlids and plecos, each claim a patch. Use rock, wood and plants to divide the floor into several areas, each with its own cave, so each fish can hold one without seeing the others all the time.
  • Cover helps, but it isn't magic. In the betta study, adding gravel, plants and a rock didn't stop two males fighting. More space reduced their displays and chasing, but even very large tanks didn't make two male bettas safe together. Layout can soften aggression; it can't fix fish that shouldn't share a tank. See aggressive fish.

Live plants or fake?

  • Live plants give cover, use up some waste, compete with algae for nutrients, and many fish spawn in them. Some need good light and nutrients to grow, and dying plants rot and foul the water. Plant-eating fish such as goldfish and some plecos will eat or uproot them.
  • Fake plants (plastic or silk) never die and need no light. Aquarium Science actually suggests beginners start with plastic plants, because a small tank with a few live plants is harder to keep than it looks.
  • A mix is fine. Many keepers start with hardy live plants plus a few fake ones, then add more live plants once the tank is settled.

Light and plant basics

  • Start with hardy, low-light plants. Java fern, anubias, cryptocoryne, Amazon swords, vallisneria and java moss are common easy choices. Aquarium Science lists several of these among the plants that keep going in well-stocked tanks.
  • Tie java fern and anubias to wood or rock. Their thick stem (rhizome) rots if you bury it in the substrate.
  • Keep the light on a timer. The RSPCA suggests artificial light for about 8 to 10 hours a day, off at night. Keep the tank out of direct sunlight, which overheats the water and grows algae.
  • Match plants to your temperature. Not every plant handles warm water. The plants section lists each plant's temperature range, light and care.
  • Floating plants shade the tank and give top fish cover, but leave some open surface for gas exchange and for air-breathing fish. They can spread fast; see duckweed.

Room for cleaning and flow

  • Leave a gap behind and around decor so you can reach in with a gravel vacuum and an algae scraper. See cleaning the tank.
  • Don't block the filter. Keep decor away from the intake and outflow so water moves through the whole tank. Cover the intake if you have small fish or shrimp; see filter intake.
  • Avoid dead spots. Tight corners packed with rock collect waste. If you see muck building up in one place, open up the layout there or point the flow at it.
  • Build on the glass, not the sand. Heavy rocks should sit on the tank floor so digging fish can't undermine them.

Products that help

  • Clay, ceramic or slate caves: sized for your cave-dwelling fish.
  • Aquarium driftwood: shelter and sight-line breaks; food for some plecos.
  • Aquarium-safe rock: for building territories and caves.
  • Hardy live plants such as java fern and anubias, with cotton thread or plant glue to attach them.
  • Silk or soft plastic plants: cover that never dies.
  • A light with a timer: a steady day and night.
  • Floating plants: shade and cover at the surface.
  • Gravel vacuum and long-handled algae scraper: to clean around the layout.
  • Filter intake sponge: keeps small fish out of the filter.

How to prevent problems

  • Plan the layout before you fill the tank: tall things at the back, an open lane at the front.
  • Choose decor for the fish you will keep. Schoolers need open water; plecos and cichlids need caves.
  • Give every territorial fish its own area and cave, with spares.
  • Test new rock and clean new wood before it goes in.
  • Start with hardy plants and add more once the tank is cycled and stable (see cycling).
  • Leave room to clean, and keep decor clear of the filter.

Why it matters

Most aquarium fish are small prey animals. In the wild they live among roots, rocks and plants, and being out in the open is dangerous. A fish with nowhere to hide stays on alert, which is stress, and stressed fish get sick more easily (see fish stress). Active swimmers need the opposite: room to move as a group. Territorial fish fight more when they can see each other all the time. A good layout gives each kind of fish what it needs, and a tank where fish feel safe is one where you'll actually see them.

When to get help

Ask an experienced keeper or your local fish store if fish are still hiding all the time weeks after setup, if fighting continues after you've rearranged and added cover, or if you're not sure a rock or piece of wood is safe. If your live plants keep melting or rotting, the plants section and a local aquarium club are good places to start.

In the game

In Multiple Tank Syndrome, plants come in the Plants pack, an add-on. Each tank has 3 plant spots, and a plant only lives within its temperature range; outside it, the plant melts. Each kind of plant does something different:

  • Hardy cover (java fern, anubias, cryptocoryne) breaks up sight lines, so bullies need a fuller tank before they attack.
  • Moss lets tiny fish (2 inches or less) hide, so predators can't eat them.
  • Tall plants (Amazon sword, vallisneria) break the current for calm-water fish, and floating plants calm the surface for top swimmers.
  • Fast growers (hornwort, water sprite, rotala) help against ammonia spikes and algae.
  • Plant eaters, like goldfish, oscars and wood-eating plecos, tear up every plant in their tank.

The "Planted tank" goal needs 3 healthy plants and 6 or more fish in one tank. The game doesn't have cards for caves, rock or wood, and it doesn't track open swimming space.

Sources

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