Freshwater Aquarium Starter Guide
A freshwater aquarium can be part of home improvement, a pastime activity for lovely moms who spend days at home or a material on biology for home-schooling. It will even be more pleasant if startup of freshwater aquarium is mistake-minimized. Anyway, for a frequent traveler, it is better not to keep fish or any other pet. Also if there is already other pet at home, it is better to avoid keeping fish lest the attention will be spread thin. Keeping fish should be easy, otherwise it cannot be considered as leisure. This is not an urgent matter so you do not have to start it immediately. A good time to set it up is when you get a free fish tank given by your neighbor who has just quit to be a tank keeper (he or she should read this), hehe. If you live in an apartment, you can tip the janitor to keep the old aquarium that someone else has discarded for you.

Benefits of an aquarium:
a) It makes home homelier. If it is kept in a classroom, it makes the class livelier.
b) Aquarium scene entertains guests. A decent aquarium always attracts eyes.
c) It can bring social activity (interaction with other enthusiasts).
d) If we have some plants at home, we can water them with aquarium water.
e) It can be used to grow some vegetables. This is called aquaponics. f) Well, it may be useful during fire (e.g. to wet a blanket) but make sure the aquarium is far from the power socket or else it can be a cause of short-circuit fire itself in case of leak.

The hobbyist mindset in setting up and maintaining a self-sustaining tank: to mimic the nature. Simulate the habitat in the interest of the inhabitants to make them as happy as possible. A tank that nearly achieves ecological balance (able to metabolize waste) can be considered a biotope. Unlike other type of petting (in rare cases a dog can get along with a cat), multiple types of organism (flora and fauna) can be kept together in an aquarium.

If you are a beginner aquarist, you should keep a log of what you have done and your observation on the fish husbandry. Focused attention on one aquarium gives more chance of success. Do not be pushed by the sudden whim to keep two or more aquaria unless you are really serious about it such as you want to do experiment or something.

Scientific name (in italic) for the ornamental fish and plants is mentioned in this article because different common names may be used between two regions. Scientific name is more specific. When you type the scientific name in any search engine, you can be sure the search result, together with fish picture, is precise.

Choosing tank
Air pump
Other things to put in
Location of the tank
Local fish store
Fish food

Choosing tank

The bottom of the tank should be reachable by hand because it is easier
a) to organize the tank.
c) for light to reach the plant at the bottom of the tank.
Tall shape is less desirable for fish compared to long shape.

It should have an optional cover as some fish like to leap out.

Fish bowl is not that good. The more water filled in after half level, the smaller the water surface area for air exchange.

How much should the minimum capacity be? It is rather subjective. Some people calculate that based on the total length of fish they want to have. Some people do not have ample space at home. Do not be influenced by others but custom to our own condition. The option of buying a tank stand / rack can be kicked out by identifying an existing strong shelf etc in the house to place the tank. Then with the size of existing support for tank in mind, we know what volume of tank we want when we are at the shop. I had 20 liters on top of a 42 centimeters width small bookshelf. Two little hardy honey gourami fish seemed to be happy with just 20 liters. Do note that bigger tank is chemically and biologically more stable and the tendency of cloudy water is slightly lower relatively so frequency of water change can be lesser. The smaller the tank is, the fewer the number of fish and the hardier the fish type should be.

Tanks with rounded corners although more expensive but they look much more better than tanks that have joined corners. Tank with joined corners have more seams so leakage has higher possibility to happen. Tank with rounded corner is usually made of acrylic. Acrylic is good if you have heater in the tank because it insulates better than glass. The drawback of acrylic is it can be scratched easily. I get a glass tank because I know I will scratch an acrylic tank when I rub algae off the tank wall.

Note that if a tank does not have a piece of Styrofoam underneath it, it must be put on a clean and even surface or else the bottom glass may break when the tank contains water.


The agitation of water surface by a filter promotes air exchange and prevents formation of thin protein (from fish food etc) film on water surface that blocks air exchange.

There are many types of filter. Each has its own strength and weakness. For example a canister filter is good at filtration but it is harder to clean.

Get an external hang-on-back (HOB) siphonic overflow power filter. External means more space in tank. It simply hangs on the edge of aquarium without any extra mounting pieces. Wet and dry exposure on its bio-wheel (if any) lets beneficial aerobic bacteria do their job effectively. The air exchange is so effective that tank water evaporates fast and regular top up is needed. Note that although internal under-gravel filter is better for bacteria colonization but it has more other weaknesses.

If the shop has a few sizes, choose the biggest one because:
a) more beneficial bacteria can dwell in it.
b) bigger impeller will not get stuck easily.
c) bio-balls for the colonization of beneficial bacteria can fit into it.
d) since the water flow is not strong, the bigger the diameter of the siphon tube the better so the siphon tube cannot be easily clogged by leaves from your plant etc. Then you do not have to always take out the siphon tube and let strong tap water enter the tube to flush out the debris.

hang-on filter
Hang-on-back filter

At the shop check that the filter pad must not be made of floss that has easily detachable filaments. I like porous element that has shape memory. Also ensure the U-shaped suction tube slides into the mounting groove on the filter perfectly and caps on the impeller without much effort. Do not buy the one with ultraviolet ray because it defeats the purpose of biological filtration. If there are two options of price, buy the more expensive one because the motor is stronger and more durable.

Fill the filter with water first so that the siphoning action works later. Switch on the power. The power is just enough to siphon up water from the tank to fill up the filter until the water overflows naturally into the tank like a tiny waterfall thus there is no motorized strong current that agitates the fish. The water bath with just right water movement (not idle but yet not strong) in the filter is ideal for nitrifier colonization besides the bio-wheel. Put small rounded stones or bio-balls into the filter to increase the colonization surface. The water level in the tank should not be too high so that the tiny waterfall from the filter splashes more water movement in the tank, which means even more air exchange and closer to nature.

The filter pad should be rinsed in the water that is scooped out of the tank for change, not in tap water to preserve the beneficial bacteria. Do not throw the filter pad away because beneficial bacteria are developing on it. The filter pad needs not to be replaced unless it has become torn. Bio-filtration improves with age so do not wash the filter. Always watch water level to ensure the tip of the siphon tube is underneath water surface. If there is no water in the filter, not only the motor will heat up, the bacteria colony in your filter also will be destroyed. Just in case if this happens, turn off the power immediately to let the motor cool down and it may still function. Take out the impeller to see if it is tangled by something (I discovered human hair on 28 Aug 2006). If it stops for a few hours, the water actually starts to turn cloudy. And you will start to amaze at the efficiency of this simple filter without much filtering material in which you doubt it when you first open the package. If the flow rate decreases after a few weeks, thoroughly flush the siphon tube. Also take out the magnetic impeller to brush and wash away the slime.

The filter inlet should be sleeved with a filter sponge. This gives an extra level of filtration before the water enters the filter. Shrimps and fries, if any, will also be protected from being sucked into the filter.

If you keep Goldfish or other bigger fish, heavy filtration (for example two filters) is needed. Or change to a more powerful filter.

Never let the filter operate with bare inlet tube without the strainer (the cap at the end of the inlet tube that looks like a tiny basket). Fish may be sucked into the tube and die.

Air pump

I talk about air pump after filter is because it is an optional supporting tool to filter to further aerate the water. The smaller the tank the bigger the need of having an air pump for aeration because less water means less oxygen. Oxygen is also needed by plants when there is no light. Plus the bubbles look cool too, hehe. I personally like to put the bubbles at front left or right corner.

Note that on the other hand, carbon dioxide will dissolve less in water agitated by air bubbles. This will reduce the growth of submerged plants.

Choose the shop that gives you a length of air hose and an air stone for free. Why is air stone important? It
a) makes the air bubbles smaller so that more air is exchanged.
b) keeps the air pipe from floating.

To prolong the durability of the pump, turn the air pump to the max only when there seems to be something wrong with the tank environment.

If you dislike the pump vibration rattling noise and you have extra money, go for an aerator. Some even have lighting for the bubbles. Silent air pump is also available.

An air-driven sponge filter can be by done DIY. Sponge filter is good for shrimp or fry tank.

By the way, if you do not keep an anabantoid but you see a lot of suds (tiny bubbles) on the water surface, it just indicates that a water change is needed.

Besides viewing pleasure, lighting is essential for underwater plants. It also helps a little in maintaining water quality by releasing some gases out of the water.

If the light is unsuitable for plant, the aquatic plant will hardly survive. The power should be around 120W. Brighter light also makes the tank look great. For green plants, color temperature of the light should be warm white (around 2700 Kelvin).

UV sterilizing light should not be used as it may eliminate the nitrosifying and nitrifying bacteria in new tank. They are photosensitive, especially to blue and ultraviolet light.

If your tank does not have a lid that houses the lamp and the fish you are going to keep will not leap out even without cover, choose light fixture that looks like a reading lamp that is clipped on the edge of the aquarium and has flexible neck. The flexible neck must be made of stainless steel. It is easier for you when you want to clean the tank, just turn the the lighting hood away. Also to avoid spooking the fish, before switching it on you can turn the lamp away and then turn the lamp slowly to the aquarium again after switching it on. Submersible lamp is not that good because it makes tank cleaning awkward.

Switch off the light if you are not going to see the aquarium again for the rest of the night. Also note that there is no point to switch on the light when the water is cloudy or green.


Underwater plants are essential because they:
a) absorb nitrate from the tank water. If there is no plants in the tank, artificial method may be needed to get rid of the nitrate (e.g. eliminating the source of nitrate, ammonia, by using zeolite).
b) may help to a small degree with stunting algae as they draw much more nitrate.
c) provide hiding place for fish. Fish do not really like to swim in open water.
d) produce oxygen when there is light.

For beginner, get plants that are planted on wood or stone instead of the ones that need to be planted in gravel because
a) these plants are usually hardy.
b) if the plants need to be planted in the gravel then the gravel layer needs to be thick. Thick gravel layer accumulates more dirt, unless vacuumed weekly.

Note that plants that grow on wood prefer to have water flow. Also note that the wood may release tannin into water and the water becomes yellowish (not cloudy). This does not affect water quality but if you do not like the color, put activated carbon in the filter.

For me hardy plants need less light, no fertilizer and no extra carbon dioxide. Examples are java moss (Taxiphyllum barbieri) and lace java fern (Microsorum pteropus var. windelov).

Java fern (Microsorium pteropus) and anubias do not need much light and will survive without artificially added carbon dioxide. However, they need more carbon dioxide to grow well and propagate.

There is a fine-leaved plant that is rather fast-growing if there is extensive sunlight. It grows free floating or rooted. Its proper name is Egeria densa. Other names: Elodea densa (but it is not really elodea because it produces 2 to 4 flowers but Elodea only 1, and it has large white petals versus small on Elodea, and it is good for cool to tropical aquarium whereas elodea is good for cool only), Anacharis densa (but actually anacharis is a general name for both egeria and elodea). Moniker: waterweed, Brazilian elodea.

Floating plants like water lettuce (Pistia stratiotes) and water hyacinth (Eichhornia sp.) are not really suitable for indoor aquarium because they need extensive sunlight. But those plants can absorb nitrate from the aquarium. You can take out plants that need a lot of sunlight to put under the sun once a week or you can buy a few extra bright botanical lamps.

All submerged plants are to be put at the background for better view.

If you are in a hot country, you should install a small fan to blow at the water surface to cool the water down or else the plants may die. You can buy an AC to USB wall plug and a USB fan for this.

Note that if you keep goldfish, the plants will be easily stained by goldfish's excrement even with heavy filtration. Also plants may be covered by algae but you cannot keep an algae eater with a double-tail goldfish because the algae eater may harass the slow-moving double-tail goldfish. You will need to brush the stain off the leaves occasionally to reveal the greens. Also goldfish may bite roots that are exposed, causing the plant to die. Goldfish will eat plants with fine leaves.


Gravel is needed because it is to be colonized by nitrosifying bacteria (i.e. Nitrosomonas europea) and nitrifying bacteria (genus Nitrospira, previously commonly thought to be Nitrobacter. Nitrobacter does well in soil instead). Nitrosifying bacteria oxidize ammonia to nitrite while nitrifying bacteria process nitrite to less harmless nitrate. Simple biochemistry. Gravel which has naturally smoothed and rounded surface is better for colonization. Also fish discharge will not look so apparent on the tank bottom.

Do not choose gravel that
a) has powdery surface because it may make tank water cloudy.
b) is dyed or coated. It is not natural. Also the color may leach into the water.
c) has pointy surface. Bacteria colonization will not be effective and the fish may get scratched.

I personally like naturally rounded light-colored and semi-transparent mixture small gravel with average diameter 3 mm.

Sand is for advanced aquarist (who want to keep plants that need to be planted onto substrate) because it has more considerations to take care of such as it has insufficient gap (less aerated) for beneficial bacteria to colonize, easily gets packed up together with dirt (and develop harmful matters) and may be sucked into the hang-on filter jamming the impeller. You may riddle the gravel with a shallow plastic basket as a coarse sieve (choose your own desired pore size) to separate out sand and tiny gravel.

The gravel layer should not be too thick (max 1 cm) as I explain in 'Plants' section above. It can be be thicker if the gravel is put in a container (preferably transparent) and the gravel container is put in the aquarium. It will be easier to maintain this way.


Other things to put in

With plants and light, the aquarium already has good appearance. Stone and shell are not essential in aquascaping. A few ornamental stones are OK but do not overdo it. And you should shift the stones from one corner to another sometimes because dirty things may accumulate under the stones so you want to aerate the spot. Snail shell may develop something bad inside it. Dead fish may also trap and rot inside too. Most shells are from saltwater and it is kind of odd to put some saltwater shell in the freshwater aquarium.

If the aquarium is big enough, put in an opaque channel, coconut shell or ceramic tile etc to create a cave. Fish like caves.

Put in sinking wood if you intend to keep a pleco.

Location of the tank

Do not put the tank near the place where we will walk always (e.g. beside the exit of a corridor, beside a door).


So now you have set up a tank. New tank syndrome must be alleviated. Let the tank stabilizes itself first with the equipment switched on (including light) a few days before adding fish. This lets the tank environment stabilize and lets the plants establish roots. Add at most three hardy fish first for example Black-skirt Tetra or Siamese Fighting Fish (but you can only keep one Siamese Fight Fish in a tank). Then add more fish slowly after one week. Do not add many fish at one time to prevent ammonia spike. Do not overcrowd the tank. My own reference for fish number estimation is the tank bottom available area. I ask myself this question: "Is there enough area for every fish to sleep?". Another question is: "Will there be enough oxygen for all the fish if in case there is power or equipment failure?"

Local fish store

Choose an LFS that allows you to return the healthy fish within a week if the fish is not compatible with its tank mate.

Price of fish at aquarium shop although higher than market but
a) you can choose fish and number of fish.
b) you can get the water from the fish tank itself. A fish that is put into new water will be physically shocked and may die the next day after reaching home although it still swims actively on the first day. It is a tactic for repeating sales.
c) the oxygen is new as the bag is not pre-packed as most hawkers in the market do.
d) you can build up the relationship with the shopkeeper and ask for something extra or discount from time to time.

We can even buy from local fish breeder at cheaper price. More fish varieties are available at the farm. The fish at the hatchery are also healthier because they did not go through the rugged transportation and mishandling by some LFS (such as giving wrong food or no drip acclimation). But usually there is minimum purchase at the fish farm and no choosing allowed.


What do you want? Do you prefer fish that swims
a) around actively even you do not approach the tank?
b) just a little even it is totally healthy?

For me I think when the fish with sucker mouth is sucking the tank wall, its mouth movement seen thru the glass looks cute so I will get one of those right after algae appear on tank wall. I also like to have some unexpected babies in the tank so I will get livebearers. If you are in temperate zone and you want an unheated tank, you can choose goldfish. If you like chasing scene, try Tiger Barbs. Aquatic creatures are really exotic.

Do not choose fish that
1) lives in saltwater (they are for pro only).
2) are carnivorous (such as bumble bee goby, puffer) except betta because betta can take pallet food.
3) do not eat cheap pellet food.
4) can grow to more than half foot for example single-tail goldfish, common Pleco etc unless you have a very big tank. Note that there are a few species of common Pleco: Hypostomus plecostomus, Hypostomus punctatus, Pterygoplichthys multiradiatus and Pterygoplichthys pardalis.
5) are for feeding big fish. Though they are cheap but they may have disease or parasite like ich. You can get them if you have a quarantine tank (high concentration of salt). Feeder fish are sold in big number but if you buy other fish you can ask the shopkeeper to give you two feeder fish for free. But they are usually single-tail goldfish that will grow to more than half foot. I still do not recommend getting such fish.
6) is not bred in the farm but caught from the wild.

Healthy fish
a) do not swim by wiggling like snake compared to the other fish of same kind.
b) do not have torn fin.
c) have all fins stretched out vigorously.
d) have good appetite. You definitely want to pick up fish that seems to be eating something from the bottom or the wall inside the aquarium. Do not settle with fish that is inferior. I once bought more than 10 Guppies but I was satisfied with only 2.

Each category of fish usually has many varieties to keep you busy collecting. You should decide what category of fish tank you want to have. Example:
a) Guppy (Poecilia reticulatus) tank.
b) 'Smaller Tetra' tank. Although they are compatible with Guppy too but they are less hardy than Guppy so I do not put them in one tank with Guppy. Example of smaller Tetra is Neon Tetra.
c) Endlers (Poecilia wingei) tank. It should not be mixed with Guppy as cross-breeding produces infertile offspring.
d) A tank with Platy (Xiphophorus maculatus), Molly (it needs a little salt), Long-fin Swordtail (Xiphophorus hellerii), Dwarf Gourami (Colisa lalia), Long-fin Black-skirt Tetra (Gymnocorymbus ternetzi), Long-fin Rosy Barb (Puntius conchonius, some say it is not compatible with Black-skirt Tetra but I think it is OK), Albino Red-fin Shark (Epalzeorhynchos frenatus).
e) Fantail goldfish tank. Goldfish tank will need heavier filtration as they are very messy. Goldfish are smart for example some will let you pat on their head when they approach you. But you should not put many goldfish in a tank because when they grow up they will need a bigger tank. One goldfish for each variety is enough. Common varieties are Common Fantail, Oranda, Lionhead (it has smaller wen coverage than Oranda, only on top of the head), Black Moor, Calico, Ranchu etc. In my 20-liter tank I once had seven goldfish so the water was very cloudy. Actually 20-liter tank is good for two goldfish only.
f) Single-tail goldfish tank.
g) Tiger Barb, Gold Tiger Barb and Green Tiger Barb (All Puntius tetrazona, the original type with black stripe is hardier) tank.

Fish for cleaned tank and totally new water: Black / White-skirt Tetra. This fish is super hardy. It has sharp eyesight: it darts lightning fast to the water surface to FETCH fish pellet. Other fish do not fetch, but rather just eat the pellet at the water surface.

Fish for level 1 owner from my experience:
1) Platy. It is also called Moon. It may jump out of tank particularly after water change.
2) Long-fin Swordtail. Its hardiness is less than Platy but more than Molly. Due to its hardiness and ability to reproduce in high numbers it has become a nuisance pest as an introduced species in a few countries causing ecological damage.
3) Black Molly (Poecilia sphenops)
4) Common Fantail Goldfish
5) Tiger Barb
6) Dwarf Gourami
7) Bristle-nose Pleco
8) Colorful female Betta
9) Guppy
10) Blood Parrot Cichlid (no scientific name. It is a fish Frankenstein. Some aquarists do not want to keep this due to principle issue)

Fish for level 2:
1) Neon Tetra (Paracheirodon innesi)
2) Black goldfish (some people call it Black Moor)
3) Long-fin Rosy Barb
4) Green Tiger Barb
5) Gold Tiger Barb
6) Sailfin Molly (Poecilia latipinna)
7) Oto (Otocinclus affinus)
8) Gold Chinese Algae Eaters (Gyrinocheilus aymonieri)

Level 3: a) Discus (Symphysodon aequifasciatus)

For a tank with several types of fish (community tank), ensure that
a) the fish are compatible. Do not ask the shopkeeper. They will always say that two fishes are compatible as long as the fishes are not straightforward aggressive (somehow some fish just will not bully other fish when you are present. Smart huh?). Instead watch how the shop puts the fishes or check in the Internet for compatibility.
b) there are only two for each type with unknown gender (except Bristle-nose Pleco should come in one only because there will not be much algae for them). For fish with known gender such as platy get 1 male to 2 females (or 2 to 4, or 3 to 5).

The number of fish for one type should not be too many until we cannot count them at one glance.

If you see an interesting fish that you do not know its compatibility with other fish but you feel like buying it, do not buy it first. Get the name and check out the compatibility. You can always go back to the store next time.

Incompatibility examples from my experience:
a) Fancy Guppy, Swordtail, White-skirt Tetra (white version of Black-skirt Tetra) will nibble fancy goldfish's tail.
b) Yellow carp will nibble goldfish's tail until goldfish is killed. Yellow carp looks quite identical with single-tailed goldfish except it leaps and its eyes are further from the mouth (some have whole eye dark in color).
c) Goldfish will eat Neon Tetra and any fish fry / baby (for example from livebearers).
d) Common Pleco, Chinese Algae Eater and Otto may gasp on Goldfish's side.
e) Dwarf Gourami may starve to death due to imbalanced competition with other fast-swimmers.
f) Albino Red-fin Shark may chase fish that has similar shape and size with it and may gasp on Goldfish.
g) Sailfin Molly and Platy will starve to death if fed with pallet food and kept with Goldfish because they cannot hold the pellet with their mouth.
h) Somehow only one Platy will survive if a group of Platy is kept with Goldfish.

Note that if you keep fish that may jump out of the tank (such as Neon Tetra, Platy, Swordtail), the water level should not be too high or the tank should be covered.

To avoid waste of money buying fish, do NOT mix Goldfish with other fish. It is a rare occasion that other fish is compatible with Goldfish. The temperature need is different too because Goldfish is coldwater fish while tropical fish is from warm-water.

An Asian Freshwater Clam (Corbicula fluminea) can be kept too. It scavenges on the waste in the aquarium.

This manual is more than adequate for some super hardy fish, such as Siamese Fighting Fish (Betta splendens).

Fish food

For healthy fish we should have at least two brands of fish food. The fish food should contain plant matter (such as spirulina). The food should not contain colorant and other chemicals (such as synthetic compound that is said to enhance the color of fish). If you have bottom feeder such as corydoras, do not choose food that stays afloat. The smaller the pellet size the better even for big fish like Goldfish because it is easier to digest so the chance of suffering from swim bladder disorder (SBD) is lower. Take a look at the pellet size before paying for the food bag at the shop because the pellet size may vary although the packaging is alike. Also feed the fish with frozen bloodworm once a week. Tubifex worm is not recommended because it is dirty: it lives in sewers and drains.

tiny coffee spatula
Tiny plastic coffee spatula

To have better control of the amount of food you feed in, you can use a tiny plastic coffee spatula. It is small enough to be put inside fish food bag. Some fish food bottles come with a small spoon.

If you will be away from home, buy food block. The longer you are away, the bigger the block. On the label you can see the number of days the block will take to fully dissolve. Please note that the food block may cloud the water. Get an auto feeder if you will be away from home for more than two weeks.


Pick up a packet of aquarium salt too. Occasional addition of aquarium salt is not bad. Salt neutralizes excessive nitrite, helps fish that have scales build protective slime / mucus coat, promotes healthy gill and kills parasites. Do not use table salt because it may contain unnatural additives like anti-caking agents (to smoothen granular flow) sodium ferrocyanide. Note that scaleless fish (like Pleco), tiny fish (for example Neon Tetra or baby fish) and some plants may not tolerate salt solution. And do not let salt crystal drop on plants. Also, some manufactured fish food contains significant amount of salt.

If you keep aquatic invertebrates you should get aquarium iodine. Do not put activated in filter or use foam fractionator (aka protein skimmer - a type of filter) because it will remove trace of iodine. Aquatic invertebrates that are usually kept in the aquarium are shellfish (crustacean and shelled mollusk). An example of crustacean is shrimp. Clam and snail are categorized under shelled mollusk.
Posted: 2007-01-20; updated: 2017-06-27 by Ong Seng Aun.
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