This is a walk-through of the basic techniques around aquarium filtration and how they apply to betta tanks.


This information also applies to community tanks of all kinds, but is more focused on freshwater than saltwater tanks.

Filtration is optional for a single betta bowl

If you have just one betta in a bowl or aquarium, you don’t need to get a filter. Personally, I don’t like the noise a filter adds, and one of the finest things about keeping a betta a bowl without a filter is the silence. If you skip the filter, though, you will need to stay on top of water changes. A two gallon bowl should have a complete water change every 7-10 days. Five gallon aquariums should have 50% of the water changed once a week.

When to get a filtration system

If you’ve got a community tank, you ought to get a filter. Also, if you’ve got a lot of plants in your aquarium, you may need to get a filter to keep up with the inevitable leaf shedding and decomposing that goes along with having plants.

Having a filtration system does not mean you can skip doing water changes. You should still be removing 20% of the water from the tank every week and replacing it with treated tap water.

Also, filters need to be cleaned out every week or so. If you do not thoroughly rinse out the filter sponges and/on “filter media” your filter pump will have to work much harder and you will shorten your filter’s lifespan by 50% or more. A good-quality filter, treated well, can last ten years or more. One that’s neglected may break in 9 months.

Types of filtration

There are three kinds of filtration: biological, mechanical and chemical.

Biological filtration works by making use of the “good” or nitrifying bacteria that break down fish wastes into nitrate and nitrite. Biological filtration works with (and basically, is) the nitrogen cycle you learned about in the section on cycling your tank. Biological filtration is used in just about every filter available right now. It requires a lot of surface area, so sponges and other porous materials are commonly used to maximize the bacterial action.

Mechanical filtration means actually pulling bits of waste and whatnot out of the water. Usually this is done by running water through a sponge. Actually, the sponge is performing both mechanical filtration by grabbing the particles, and biological filtration as the little bacteria that live in all the crevices of the sponge break down the captured particles.

Chemical filtration means the filter is removing dissolved compounds from the water. Most fish filters focus on biological and mechanical filtration; chemical filtration is used only sparingly. You are kind of using chemical filtration when you treat tap water with water conditioner to get the bad gases and heavy metals out.

The only time you’d really need chemical filtration after water treatment is if you wanted to add a bag of activated carbon to your filter to absorb odors, or if you had an ammonia problem and wanted to put a bag of “ammo rocks” or “ammo-lock” in your filter. There are also nitrate and nitrite absorbing “rocks” or granules that you can put into a plastic mesh bag and then put into your filter.

Lighting doesn’t make sense for a simple betta bowl. Some people do put their betta bowls under table lamps, or use clamp lights. If you want to add a light, that’s fine. The only need for it would be if you have plants that require brighter light that indirect sunlight. Amazon swords, for example, will need extra light, as will many vallsineras.


If you bought a java fern or java moss for your betta bowl/aquarium, you’ll probably be fine with just indirect sunlight. Java ferns and java moss are widely considered the best plants for bettas. Some betta breeders consider java moss an essential item in the breeding and fry-raising tanks. The java moss gives the female betta a place to hide, and later it does the same for the small fry. They can also eat bits of the java moss, which takes one wee bit of that part of the job off you.

For those of us who want just a simple, low to no-tech betta bowl, natural sunlight is the best choice. While it is tempting, do NOT put your betta bowl or tank in direct sunlight. The sun will overheat the bowl during the day, and then at night your betta’s water will have a severe temperature drop. Big hikes and drops in water temperature are even harder on bettas than just being cold all the time.

Direct sunlight also seems to make many bettas really twitchy behaviorally. This does make sense – they evolved to live in ditches and to hide, so they are not used to open water in full sun, but that really is only half an explanation. I don’t know the full explanation of why full sunlight stresses bettas, but it does. Keep your betta out of full sunlight.

Nice indirect sunlight is fine, though. In this sense bettas are a wee bit like ficus trees. Ficus trees can not handle direct sunlight (it burns their leaves) but they do need a fair amount of light. Bright, indirect sunlight is good. My betta, Charlie, is in a bowl that gets bright direct sunlight. There’s an amazon sword plant in his bowl (an eclipse hex 5) that is growing better than plants I used to keep under expensive aquarium plant lights. Of course, we do have algae issues (you put a bowl in even medium sunlight and it will grow algae), so I got a snail, and when I change the water in his tank I swab the inside side down with a paper towel or two. So the algae is under control, and the plant looks great.

If you have a full-scale community tank, complete with a cover, you will need some lighting, even if your tank is next to a bright window during the day. Flourscent bulbs with a plant-friendly full spectrum are an excellent choice. Metal halides are for serious fishkeepers who want to do aquascaping. A good quality fluorescent bulb will cost around $20; metal halide setups start in the hundreds of dollars.

Get yourself a nice cover for your aquarium that will accommodate not one, but two rows of lights, buy good quality flourscents, and you’ll probably be OK with most medium light plants. If you get a glass cover for your tank, you’ll also be able to add another strip of flourescents later if you want to increase the light.

Aim for about two watts of light per gallon of aquarium water and you’ll have nice lush growth in your medium light plants. Do be sure to ask before you buy plants if they require high light, then if they do, pass on that plant. Leave it to the people with the expensive metal halide setups.

After all the work you’ve gone to to create that special environment inside your tank, don’t muss it up by adding a sick fish. Here’s the rub: all new fish are potentially sick fish. Even if they look great at the pet store.


Enter the quarantine tank. This is a small tank kept in addition to your large show tank. You put all new fish in there for a week to a month (some fish people really do a month) to make sure they’re healthy before you add them into your community tank with all your healthy fish.

Quarantine tanks are also helpful for fish that become sick in your community tank. At the first sign of trouble, you take the sick fish out of your display tank and put it in the quarantine tank and treat it there.

Quarantine tanks have the usual components of other fish tanks – a heater, filter, and a backup thermometer to make sure the temperature is right. Sick tanks are kept a bit warmer than normal, as this helps the fish recover faster.

I’ve kept a lot of fish over the years, and only had a quarantine tank when I had my huge planted discus tank. Frankly, I am a bit too lazy to do the full and proper screening of new fish that quarantine tanks represent. However, there is a real risk to not having one. If you do get a sick fish in your primary tank, you are then basically dealing with not one sick fish, but an entire thankful of sick fish. If you picked up a really nasty illness or infection, there is a real chance most of your fish could die.

If you have a planted tank – live plants that you may love, that you bought expensive lights for, and lovingly tend to – the consequences are even worse. Many of the medications for even common fish diseases are not plant friendly. Neither are they filter friendly – antibiotics kill bacteria. All bacteria. If you have to use a strong dose, you may end up having to recycle your filter again, or at least build it up again from 10% of its previous capacity. It can be a real pain. (Remember why I like the no-tech single betta in a glass bowl?)

All that said, I have successfully treated ich and hole-in-the-head in a planted tank. You can still treat diseased, even in big fancy planted tanks. Its just a wee bit riskier. Still, if you take the time to really inspect your fish every day, you’ll probably catch an illness before its out of control. And that can make all the difference.

If female bettas are kept in the same tank as a male betta, the chances are that over time the male betta may get it into his head to breed. He will begin to make a bubblenest and will become extremely aggressive toward any fish that comes anywhere near the bubblenest.


Even a 20 or 30 gallon tank will suddenly become much too small for your male betta’s aggression – all his tank mates will be cowering behind plants at the other side of the tank if they want to keep their fins.

Many betta keepers do have both male and female betta fish together in larger community tanks; just be aware that if your male decides to breed, you’ll need to move him to his own space.

More than one female betta can be kept in a community tank. You can have as many female bettas together as you want, so long as you’re not overcrowding. The female bettas may squabble and may occasionally tear one another’s fans but their aggression will be significantly less than their male counterparts, and it’s highly unlikely any of them will ever suffer serious damage.

Pros and cons of a betta alone

One betta in a bowl is the easiest set up for an aquarium. Most of this book is focused the best conditions for having one male betta in-a-bowl. The pros of keeping a single male betta in a bowl (or tank) are:

1) you won’t need a filter

2) you can go away for up to a week without having anyone care for your betta – he can go on a one week fast with no problems

3) cleaning the bowl and doing water changes is much easier

4) the single betta bowl is likely to take up much less space than a community tank, so you can have one in an office or even the tiniest apartment

5) small one betta bowls are inexpensive to set up and maintain

6) silence. Single betta bowls don’t need filters, so you don’t have to put up with the noise of the pump and the gurgling water. If you’re working near your betta bowl on a regular basis, or if you’re sensitive to noise, having that silence may make the difference between wanting the fish and not wanting it.

Cons off having a single betta in a bowl are that

1) you can’t have any many fish (of course) and schooling fish can be fun and relaxing to watch,

2) a single betta in a bowl is not as luxurious as a full planted tank that’s significantly larger than your little 3 gallon setup

3) smaller tanks give your betta less room to move around

4) smaller tanks need to be cleaned more often

5) smaller tanks are more susceptible to sudden changes in temperature, which can stress your betta enough so that it gets sick.

Pros and cons of bettas in a community tank

The pros are that

1) you can get a bunch of different fish (keep reading for appropriate tank mates for bettas

2) you can get a larger tank, so your betta can have more room to move around

3) larger tanks need cleaning less often, and aren’t as suspectible to sudden temperature changes

4) larger planted tanks look nicer and may give you more of a sense of actually being underwater.

Cons of having a betta in a community tank are

1) you may need a second hospital or quarantine tank because if one fish gets sick its much easier to maintain the quarantine tank than treat all the fish in the tank at once. Many fish treatments will harm plants, and some will kill off all the bacteria in a tank, including the good bacteria you worked so hard to culture.

2) betta fins tend to get nipped, sometimes by even the most placid of fish, so your betta may get banged up a bit by the other fish in the tank

3) you will have more maintenance work to do with a larger tank

4) larger tanks are more expensive to setup and maintain

5) if you need to go away for a few days, you will have to ask someone to look after your fish.