For children · Science · Biology

Aquarium biology for children: living things and activities

The fish are the part you watch. The part that keeps the fish alive is bacteria on a sponge, plants counting photons, and animals that hatched out of mud. This page tells you what each of those does, in a few sentences, and then hands you the page on this site that teaches it properly. After that come thirteen exercises, and you cannot do them without going and reading.

Ready to explore? You can read the explanations on your own from about age eight or nine, or share them with an adult. Bring a pencil for the exercises. Most use division and suit ages ten and up. Follow the links to find the numbers you need, or start with a shorter aquarium story.

Elodea leaf cells seen through a microscope
The tip of an Elodea leaf seen through a microscope.KarlGaff · CC BY 4.0 · Resized; uncropped.

Half one · the biology

Nine ideas. Each one is two sentences here and a whole page over there.

Read the two sentences first. If an exercise later asks you for a number, come back to this list, click through, and hunt for it. Every page we send you to is written for a grown-up, and that is on purpose: you are allowed to read a grown-up page, and you will find that you can.

The tiny helpers in the filter

A fish breathes a waste into the water that you cannot see, and it is a poison. Living things far too small to see eat that waste, and then eat what is left, and what comes out at the end is plant food. They live on the sponge in your filter, and nobody put them there.

How a filter startsThe same story, three ways

Who the helpers actually are

Scientists opened up real home filters and counted what lives there. They found that one kind of bacteria can do the whole job by itself, start to finish, with no partner1. They also found that the helpers are a tiny minority: nearly everything on the sponge is doing some other job entirely. And they cannot work without oxygen, in an amount you can work out from the chemistry rather than guess at.

Who does the workWhat the filter breathesWhat the filter is mostly made of

How a leaf pays for itself

A leaf makes food in the light and burns food all the time, day and night. There is a brightness where the making exactly matches the burning, and it has a name: the light compensation point. It has been measured on real submerged leaves, and it comes out as a range rather than one number4. Below it, the leaf is losing. Above it, the leaf is saving.

Light, and how much a plant needs

Two ways to take carbon

Every plant needs carbon to build itself. Some water plants can only take carbon dioxide, which is scarce in water. Others can also take carbon out of bicarbonate, which hard water is full of, and about half of the eighty species anybody has tested can do it4. Those are the plants that grow well in Armenian tap water without any special equipment.

Which plants can use bicarbonateA tank that runs on soil

Why algae want ammonium

People blame algae on nitrate, which is the safe leftover at the end of the chain. Algae would rather have ammonium, which is near the start of it, and once there is even a little ammonium in the water the algae mostly stop bothering with nitrate. So an algae problem is usually a message about the beginning of the chain, not the end.

Water, and what the tests mean

What a fish and a shrimp need from the water

A fish is an ectotherm, which means its body is the temperature of the water around it, and everything it does speeds up when the water warms. A shrimp needs the same things and one more: copper poisons shrimp, and it hides inside medicines meant for fish.

Fish, shrimp and snailsFind a fish

Warm water squeezes from both ends

Warm water holds less dissolved oxygen than cool water. A warm fish needs more oxygen than a cool one, and for the neon tetra somebody has measured by exactly how much5. Both of those move the wrong way at the same time, which is why a summer heatwave is harder on a tank than a cold night is. It is worth knowing how the oxygen gets in there in the first place, because there is more than one way and they are not equal.

Temperature, and the oxygen squeezeHow oxygen gets into a tank

How much life a tank can carry

A tank can only carry so much animal, and the honest way to count it is by weight rather than by how many fish. Liters decide how much waste the water can take. The length of the tank decides something else entirely, which is whether a fish has room to swim.

Easy setups and the weight budgetForgiving to demanding

The animals in a jar were already there

Put pond mud in a jar of water on a windowsill and animals appear. They did not fly in. Their eggs were in the mud, waiting, some of them for years. And they appear in an order, because nothing can eat until there is something for it to eat.

Make a pond jarWhat is in the mudThe order things appear in

A shoal is a sense, not a number

Fish hold a group together with two senses at once: their eyes, which stop them drifting too far apart, and a line of tiny organs down each side that feels water moving, which stops them crowding too close. Knock out the second one and the group spreads, stops turning together, and starts bumping, and every step of getting better again has been followed day by day6.

What a shoal isThe whole living system

One idea worth getting right

What is really in a filter, and why the shop's version is older than the evidence.

Here is a thing you can know that most adults in this hobby do not.

Most books and most shops tell the story of the filter as two named bacteria, one for each step. It is a tidy story and it is what the label on the bottle says. People went and looked inside real home aquarium filters, and it is not what is in there.

In 1998 a team sampled working freshwater aquarium filters. The organism named on every shop explanation was not detected at all, and a completely different group of bacteria was doing that step instead2. The same group later showed the first step was misnamed too3. And look inside home aquarium filters with modern methods and you find organisms that carry the ammonia all the way through to nitrate by themselves, with no partner at any stage1. Those have a name, and the exercises will send you to find it.

So the honest sentence is the simple one. There are tiny helpers, they live on the sponge, and they clean the water. That is closer to what is really in your filter than any list of two names, and it is the version this hub writes for children for exactly that reason. It is not a simpler story told to a child. It is the more accurate one.

What to do with this

Two exercises below turn on it. Before you start them, read how a filter starts and who does the work, and write down two things: what the 1998 team looked for and did not find, and how long a filter really takes to be ready.

Half two · the exercises

Thirteen exercises. Each one is missing a number, and the number is on a page.

Every exercise is built the same way: a situation, then the numbers you are given, then the task. Something needed is deliberately not printed, and the link at the bottom of each exercise tells you which page is holding it. Work in a notebook, write the number you found and where you found it, then do the arithmetic.

Where an exercise asks you to decide rather than to calculate, a bare yes or no does not count. Write the reason, and name the evidence you are resting it on.

Exercise 1

Warm-up · percentages

The filter census

Anahit has had her tank running for a year. She squeezes the filter sponge out into a bucket of tank water, the way you are supposed to, and the water goes brown and cloudy. Her uncle works in a laboratory, so she asks him what is in the cloud. He counts it properly and tells her there are five million living things in the sample. Anahit assumes they are all the helpers that clean her water. Her uncle says that is the interesting part, and sends her to look it up.

Given

  • Organisms counted in the sample: 5,000,000
  • The sample came from a mature home biofilter sponge
  • Three home filter sponges have been measured and published; the share of them that are ammonia oxidisers is on the page below

Task

  1. Find the three measured sponge percentages. For each one, work out how many of Anahit's five million are ammonia oxidisers.
  2. Using the smallest of the three, how many of the five million are doing some other job? Write it as a number and as a fraction of the form "about one in N".
  3. The same study measured a different filter material with a much wider range. Find that range, take its top end, and check the claim this site makes that at least six in seven of a filter are not ammonia oxidisers. Does the claim hold at the top of the range?

Read: Who does the workWhat the filter is mostly made of

Exercise 2

Standard · reasoned decision

The bottle at the shop

Aram and his father are buying a tank. The shop assistant puts a small bottle on the counter. The label says it contains two named bacteria, one for each step of cleaning the water, and promises the tank will be ready to take fish tomorrow. It costs about as much as two plants. Aram's father is ready to buy it, mainly because waiting is boring. Aram has read the pages below.

Given

  • The label names two bacteria and assigns one step to each
  • The label promises the tank is ready in one day
  • Two studies of real aquarium filters, and one modern survey of home aquarium filters, are described on the pages below

Task

  1. Name the organism the 1998 study went looking for and did not detect, and name the one it found doing that step instead.
  2. Name the kind of organism that modern surveys find carrying the whole conversion from ammonia to nitrate on its own.
  3. Find the honest range of time a home filter takes to be ready, as measured in real home tanks, and write it down. How many weeks apart are the fastest and the slowest?
  4. Decide. Does the label describe what is actually in a home filter? Write your decision in one sentence and support it with the two findings above. Then write one sentence on what Aram should say about the one-day promise.

Read: How a filter startsWho does the workThe same story, three ways

Exercise 3

Standard · compare with a range

Three spots on the sand

Lusine borrows a light meter from her school. It measures PAR, which is the light a plant can actually use, counted as photons landing on a square meter every second. She takes it into the tank in a sealed bag and reads the light at the sand in three places: once in the open, once under the edge of a big leaf, and once right at the back behind a rock. She wants to plant a small carpet plant somewhere and she wants to plant it once, not three times.

Given

  • Spot A, behind the rock: PAR 18 micromoles per square meter per second
  • Spot B, under the leaf edge: PAR 45
  • Spot C, in the open: PAR 120
  • The light is on for 8 hours a day

Task

  1. Find the measured light compensation point for a submerged leaf. It is given as a range, not a single number. Write the range down.
  2. For each of the three spots, decide which of these is true: the leaf is below the whole range, inside it, or above the whole range.
  3. One of the three spots cannot be settled from this range alone. Say which one and explain in one sentence why a range makes that spot undecidable.
  4. Lusine wants to plant once. Which spot do you tell her to use, and why?

Read: Light, and how much a plant needs

Exercise 4

Harder · ratios from a range

Two plants in the same hard water

Yerevan tap water is hard, which means it carries a lot of dissolved carbonate. Davit has a tank of it with no carbon dioxide equipment at all. He buys two plants on the same day from the same shelf. Six weeks later one of them has doubled and the other has gone thin and pale. The shop tells him the pale one is a "difficult plant". Davit is not sure that is the real answer.

Given

  • Both plants are in the same tank, the same water, the same light
  • No carbon dioxide is being added
  • The water is hard and full of bicarbonate
  • Eighty freshwater flowering plant species have been tested for what carbon they can use; the results are on the page below

Task

  1. Find what fraction of the eighty tested species can use bicarbonate, and turn that fraction into a number of species.
  2. Find the percentage of the dissolved carbon a bicarbonate user can strip from the water, and the percentage a plant that can only use carbon dioxide manages. Both are ranges.
  3. Work out how many times more carbon a bicarbonate user can take, first using the bottom of each range, then using the top of each range.
  4. Your two answers to part 3 are very different. Write one sentence saying why the answer has to be a range and not a single number.
  5. Name two plant genera the page recommends for hard water, and write one sentence on whether "difficult plant" was the right explanation for Davit's pale plant.

Read: Which plants can use bicarbonateA tank that runs on soil

Exercise 5

Standard · threshold

Two tanks and one green wall

Two friends in the same building both get algae on the back glass in the same week. They test their water and the results are almost opposites. Sona's tank reads high on nitrate and nothing at all on ammonium. Vahe's tank reads low on nitrate and a small amount of ammonium. Sona announces that nitrate causes algae, buys a nitrate remover, and tells Vahe his tank is fine.

Given

  • Sona's tank: nitrate 40 mg/L, ammonium below what her kit can detect
  • Vahe's tank: nitrate 5 mg/L, ammonium 0.05 mg/L
  • Both tanks have the same light, on for the same hours

Task

  1. Find the ammonium concentration above which algae essentially stop using nitrate. Write it down with its units.
  2. How many times over that figure is Vahe's reading?
  3. The page describes a test where nitrate was added as a fertiliser salt and no bloom followed, while a much smaller amount of nitrogen given as ammonium did produce one. Find that fraction and write it out, as in "one N-th as much nitrogen".
  4. Decide. Which tank is the one with the algae problem that the test kit explains, and which friend has bought the wrong product? Support it with the threshold from part 1.

Read: Water, and what the tests mean

Exercise 6

Standard · budget arithmetic

Tigran's shopping list

Tigran has saved up for a 54 liter tank. It is 60 centimeters long. The flat has no air conditioning, so in July the water sits at whatever the room does. He writes a shopping list: a group of harlequin rasboras, because he likes how they move, and one catfish, because somebody told him a catfish cleans the tank. He wants to know how many rasboras he can have before he goes to the shop, so that he does not decide in front of the tanks.

Given

  • Tank: 54 liters, base length 60 cm, no cooling
  • Adult harlequin rasbora: about 1.1 g each
  • The catfish he is looking at: about 12 g when adult
  • This site uses a stocking budget in grams of adult fish per liter, set for the July water temperature. It is on the page below.

Task

  1. Find the stocking budget in grams of adult fish per liter. Work out Tigran's total budget in grams.
  2. Take the catfish out of the budget first. How many grams are left for rasboras, and how many whole rasboras is that?
  3. Suppose he picks a bigger catfish instead, one that reaches 40 g. What happens to the budget? Write the number and say what it means.
  4. Liters answered one question here. The species finder says liters cannot answer the second one. Name the second question, and say which given number above is the one that answers it.

Read: Easy setups and the weight budgetFind a fish

Exercise 7

Harder · two effects at once

The heatwave

The same 54 liter tank, in August. The flat gets hot and stays hot for a week. The water was 24 degrees in the morning and is 30 degrees by the evening, and it does not come back down overnight. The fish hang near the surface and breathe fast. Tigran's mother says they are hot. Tigran wants to know whether they are short of oxygen, and by how much, because "they look hot" is not a number.

Given

  • Water goes from 24 degrees to 30 degrees
  • The tank is in Yerevan, at about 1,113 meters above sea level
  • The fish are neon tetras, which have been measured properly
  • Both the oxygen a tank can hold at Yerevan air pressure, and the measured temperature quotient for the neon tetra, are on the page below

Task

  1. Read the oxygen the water can hold at Yerevan pressure at 24 degrees and at 30 degrees. By what percentage does the supply fall?
  2. Find the measured temperature quotient for the neon tetra. A temperature quotient tells you the factor by which demand changes for a ten degree rise. Use it to work out the factor for this six degree rise. You will need a power that is not a whole number, so use a calculator.
  3. Put the two together. By what factor is the tank worse off, counting supply down and demand up at the same time? Express it as "about N times worse".
  4. Every stocking table in every aquarium book is written for sea level. Find, on the same page, roughly how much less oxygen a Yerevan tank holds than the same tank at the coast. Decide whether Tigran should follow a book table exactly, and justify it with that percentage.

Read: Temperature, and the oxygen squeezeFish, shrimp and snails

Exercise 8

Harder · a budget with a hidden rate

The plant on the windowsill is not a water change

Narine reads that a pothos with its roots hanging in the tank takes nitrogen out of the water. She hangs one over her 30 liter tank, it grows beautifully, and she stops doing water changes altogether. She tells everyone the plant is her filter. Three months later her nitrate test is higher than it has ever been and she cannot work out why, because the plant is clearly growing.

Given

  • Tank: 30 liters
  • Total weight of her fish: 60 grams, fed normally
  • One well-grown pothos on a bright windowsill
  • She has never cut the plant
  • The daily nitrogen a pothos removes, and the nitrogen load of a stated weight of fish, are both on the page below

Task

  1. Find the nitrogen one well-grown pothos removes per day. It is a range. Find also the weight of fish the page says that matches.
  2. The page gives the daily nitrogen load of a 15 gram fish load in milligrams. Use it to work out the load per gram of fish per day, then the load from Narine's 60 grams.
  3. Compare. Does the plant cover her tank? Give the shortfall in milligrams per day, and the percentage of her load the plant covers at its best.
  4. Explain in one sentence what the page means by "uptake is not export", and say what Narine has to do for the nitrogen to actually leave her flat.

Read: The pothos, and what it really removes

Exercise 9

Standard · prediction from a rate

Two jars on the same windowsill

A class sets up two jars on the same day, in the same light, at the same temperature. Jar A is two liters of rainwater with three dry oak leaves in it. Jar B is the same, plus a handful of sediment scooped from the top few centimeters of a pond. The teacher asks the class to write down, before anything happens, what each jar will contain in four weeks. Half the class says both jars will end up the same, because the air is full of tiny things.

Given

  • Jar A: 2 L rainwater, 3 oak leaves, no sediment
  • Jar B: the same, plus pond sediment weighing 100 g wet, which is about 40 g once dried
  • Both jars are on the same windowsill at about 20 degrees
  • A published experiment measured how many animals hatch out of sediment, per gram of dry sediment, per week. It is on the page below.

Task

  1. Find the measured emergence rate for the commonest animal in that experiment, per gram of dry sediment per week. Use it to estimate how many of that animal Jar B might produce in one week.
  2. The measured emergence ran from zero up to that figure. Rewrite your answer to part 1 as a sentence that is honest about what kind of number it is.
  3. Predict what Jar A produces, and support it with the sentence the page uses about where the animals come from.
  4. Find the order in which organisms appear, and the reason the order is that one and not another. Name the four steps of the eating chain, from the dissolved carbon upwards.
  5. One of the two jars can show the full sequence. Say which, and say in one sentence why the other cannot.

Read: What is in the mudThe order things appear inMake a pond jar

Exercise 10

Harder · two limits that disagree

How many zebrafish

Gor has a 20 liter tank and wants zebrafish. The shop tells him the rule is a minimum of six, and that six is what his tank can take. He goes home and finds two different numbers on this site. One comes from a nine week laboratory study of zebrafish held at five different densities. The other comes from a weight budget worked out for a tank with no cooling in an Armenian summer. The two numbers are nowhere near each other, and Gor has to pick one.

Given

  • Tank: 20 liters, no cooling
  • Adult zebrafish: about 0.6 g each
  • The laboratory study measured cortisol, aggression, distribution and growth together

Task

  1. From the shoaling page, find the one density at which the study measured harm, and find the band of densities the authors said cost the fish nothing. Convert both ends of that band into a number of fish for 20 liters.
  2. From the weight budget, work out the gram allowance for 20 liters and how many whole zebrafish that allows.
  3. Your two answers disagree by a lot. For each one, say what it is a limit on: the water, or the fish's social needs.
  4. Decide which number Gor should actually stock to, and give the reason in one sentence. Then say what the same page found about where the real improvement in a small group appears, and whether it appears at six.

Read: What a shoal isEasy setups and the weight budget

Exercise 11

Standard · reading a timeline

The fish look fine

A school aquarium is treated with an antibiotic for a fin infection. The treatment works and the fins heal. Two weeks after the course finishes the fish are eating, their color is good, and to the class they look completely normal. But the group is spread much wider than it used to be, the fish no longer turn together, and every so often two of them bump into each other hard enough that one stops moving for a second. The teacher asks the class to work out whether the fish have recovered.

Given

  • The antibiotic course finished 14 days ago
  • The fish eat normally and look healthy
  • The group is wider than before and no longer turns together
  • An experiment exists in which the same sense organ was knocked out and the recovery was followed day by day, with the organ's regrowth checked under a microscope. It is described on the page below.

Task

  1. Name the two senses that hold a shoal together, and say which one sets the far limit between neighbors and which sets the near limit.
  2. In the experiment, the shoal radius grew from its control value to a measured value. Work out the factor by which it grew, to two decimal places.
  3. Write out the recovery timeline: the days on which shoaling reappeared, the day the spread went back to normal, the day collisions stopped, and the day the turning-together matched the control fish.
  4. Decide. The class wants to say "they look fine, so they are fine". Using the timeline and today's day count, say whether that is safe, and name the day number the class should actually be waiting for.

Read: The whole living systemWhat a shoal is

Exercise 12

Standard · three decisions

The shrimp tank and the bottle of medicine

Ani keeps cherry shrimp and a few small fish in an unheated tank in a normally heated Yerevan flat. Three things happen in one week. One fish develops white spots and the shop recommends a treatment. A friend offers her some blue shrimp, saying they are a different species so the colors will stay separate. And her cousin says the flat is too cold for shrimp anyway and she should buy a heater.

Given

  • The tank is unheated, in a heated flat, and sits at 19 to 23 degrees
  • The shrimp are cherry shrimp, Neocaridina davidi
  • The treatment's ingredient list includes copper sulfate
  • The offered shrimp are blue, and sold as a different kind

Task

  1. Find the temperature band given for Neocaridina davidi. Decide whether the flat sits inside it, and add one sentence on what the cool end of the band changes about the shrimp's behavior.
  2. Find what the livestock page says about copper. Decide whether the treatment may go into this tank, and say what Ani should do about the spotted fish instead.
  3. Find what the page says about the color forms of this shrimp. Decide whether Ani can put the blue ones in with the red ones and still have two colors, and give the biological reason.
  4. Rank the three problems by how quickly Ani has to act, most urgent first, and justify the top one in a sentence.

Read: Fish, shrimp and snailsForgiving to demanding

Exercise 13

Harder · a supply against a demand

Is the filter short of breath?

A school aquarium has run quietly for two years. This term the ammonia test has started creeping up. Nothing obvious has changed: the same filter, the same fish, the same food. Somebody in the class says the filter organisms must be short of oxygen, because they read that a filter that cannot breathe does not break down, it just slows.

There is an oxidator on the tank, a small sealed flask that lets out oxygen slowly over weeks. A teacher fills it, never a pupil, because the strong solution that goes in it burns skin and eyes. The class works out how much oxygen the filter actually needs, and how much the flask actually delivers, instead of arguing about it.

Given

  • Tank: 120 liters, at 25 degrees
  • The class worked out from the feeding that the tank turns over 50 mg of ammonia nitrogen a day
  • The oxidator was filled with 100 grams of the 30 percent solution
  • Two refill intervals are reported for that filling, and both are on the page below
  • The organisms that turn ammonia into nitrate are obligate aerobes, which means they cannot do it without oxygen at all

Task

  1. Find how many grams of oxygen the nitrifying organisms need for every gram of ammonia nitrogen. Write it down with its units, and write down where that number comes from.
  2. Convert the tank's daily ammonia nitrogen from milligrams into grams, then work out how many grams of oxygen the filter needs every day.
  3. Find how many grams of oxygen are in one 100 gram filling of the 30 percent solution. Find the two refill intervals reported for it. For each interval, work out the grams of oxygen delivered per day, and how many times over that covers your answer to part 2.
  4. Decide. Is "the filter organisms are short of oxygen" a good explanation for this tank's creeping ammonia? Justify it with the factor you calculated, and say whether your answer changes depending on which refill interval is true.
  5. The oxygen from that flask does not go only to the filter. Name two other things in the tank breathing the same gas, and write one sentence saying why your answer to part 4 is about the filter's share and not about the whole tank.

Read: How oxygen gets into a tankWho does the work

If you get stuck

Two things usually go wrong, and neither of them is being bad at science. The first is looking for the number on the wrong page, so read the link line at the bottom of the exercise again; it names the page that is holding it. The second is finding a range where you expected one number. A range is not the page being vague. It is the page telling you that real measurements of living things spread out, and that your answer is allowed to spread out too.

Write down where you found each number as well as the number. That is the habit that makes the difference, and you can already do it.

Continue

Where to go next.

The rest of the children's library

What a child can do at each age, what it teaches, and how to keep it safe.

Make a pond jar

Two liters, some mud and three oak leaves. The cheapest real experiment on this site, and it runs for months.

The whole living system

The grown-up version of this page: who eats what, what limits whom, and where the animals come from.

Biology, chemistry and physics together

The same tank from three directions, with every formula printed so you can disagree with it.

How this hub writes for children

The two reading bands, the rules, and the nitrogen cycle written three times at three levels.

Sources

Where the outside facts on this page come from.

  1. McKnight, M.M., Szabolcs, N., Graham, A. and Neufeld, J.D. (2025). Microbial community succession of home aquarium biofilters associated with early establishment of comammox Nitrospira. ISME Communications 5(1): ycaf212. Open access, PMC12704419. The source for comammox organisms carrying the whole conversion alone, and for the measured share of a home biofilter that is made of ammonia oxidisers. DOI 10.1093/ismeco/ycaf212
  2. Hovanec, T.A., Taylor, L.T., Blakis, A. and DeLong, E.F. (1998). Nitrospira-like bacteria associated with nitrite oxidation in freshwater aquaria. Applied and Environmental Microbiology 64(1), 258 to 264. Open access. The study that sampled working aquarium filters and did not detect the organism the hobby names. DOI 10.1128/aem.64.1.258-264.1998
  3. Burrell, P.C., Phalen, C.M. and Hovanec, T.A. (2001). Identification of bacteria responsible for ammonia oxidation in freshwater aquaria. Applied and Environmental Microbiology 67(12), 5791 to 5800. Open access. The first step of the shop's story, checked against real filters. DOI 10.1128/aem.67.12.5791-5800.2001
  4. Pedersen, O., Colmer, T.D. and Sand-Jensen, K. (2013). Underwater photosynthesis of submerged plants: recent advances and methods. Frontiers in Plant Science 4: 140. Open access. The measured light compensation point of a submerged leaf, and the bicarbonate result across eighty tested species. DOI 10.3389/fpls.2013.00140
  5. Cooper, C.J., Mueller, C.A. and Eme, J. (2019). Temperature tolerance and oxygen consumption of two South American tetras, Paracheirodon innesi and Hyphessobrycon herbertaxelrodi. Journal of Thermal Biology 86: 102434. Paywalled; abstract free on Europe PMC. The measured temperature quotient for the neon tetra, which is what makes the heatwave exercise a calculation rather than a guess. DOI 10.1016/j.jtherbio.2019.102434
  6. Faucher, K., Parmentier, E., Becco, C., Vandewalle, N. and Vandewalle, P. (2010). Fish lateral system is required for accurate control of shoaling behaviour. Animal Behaviour 79(3), 679 to 687. Author version open at the University of Liege repository ORBi, handle 2268/31748. The shoal radius measurements and the day by day recovery timeline. DOI 10.1016/j.anbehav.2009.12.020