Betta fish and bowls are often portrayed as a perfect match. Unfortunately, this is not often the case, as bowls sold with bettas are normally too small to keep fish alive. While it is possible to keep fish healthy and happy in bowls, the standard fish bowl will not work.
The amount of time a betta can live in a bowl is dependent on the size of the bowl, heater, filtration, and the care you give your fish. The standard bowls sold with bettas range from 2 cups to 7 gallons, so there is no blanket statement for how long one can live. That being said, since most bowls are so small, bettas can only live for 2 weeks to 6 months in one of these, which is much less than their typical 4-7 year lifespan.
In this article, we will discuss ammonia poisoning, nitrite poisoning, nitrate poisoning, filtration, heating, and swimming space.
Ammonia is the first stage in the nitrogen cycle, and as some may know, it is a strong cleaning agent. As you may imagine, it is not a good thing to have in a fish tank. So where does it come from?
Fish waste and decaying matter decompose into ammonia, which is the first step in the nitrogen cycle. It is later processed into nitrite and nitrate, the latter of which is much less toxic. In order to be converted, it takes around a month for bacteria colonies to grow to match the bio load in the tank.
However, in a small bowl, the bacteria colonies will not be able to convert all the ammonia produced into toxic nitrite and less toxic nitrate in a timely manner. This is simply because there is not enough water to dilute the compounds to a point where the bacteria can convert all the ammonia.
In addition, ammonia can also poison the bacteria that convert nitrites to nitrates, so you will end up with an excess of ammonia and nitrite and no nitrates, and the fish will die if left in this situation.
Ammonia poisoning leaves black chemical burns on fish, and these only start to appear once the healing process begins. It will burn off scales and fins as well as cause severe damage to the gills, which often results in a fish suffocating and drowning. This is truly a nasty way to go.
As previously mentioned, nitrites are a more toxic nitrogen compound that occurs after ammonia in the nitrogen cycle. This poisoning does not leave chemical burns, but since a nitrite spike occurs after an ammonia spike, the fish will probably already be suffering from burns as well.
Nitrite binds to hemoglobin in the blood and prevents it from carrying oxygen. As you know, oxygen is circulated throughout the body through blood, and if this method fails, the animal will suffocate and die.
If the belly of a fish affected by nitrite poisoning turns red, it is too late to save it. Seeing fish gasping at the top of the water, or at the bottom barely moving is a good sign that you should test for ammonia and nitrite. If you have one or both, do water changes until they are at or below 0.25ppm.
For excess nitrites, move your fish to a separate heated container, which can be as simple as a Sterilite shoe box, and add a methylene blue solution. Dose for the bath solution, add a bubbler and move your fish in there for a few days.
Ensure the temperature remains high enough for bettas (78-82) and do not feed your fish during this time period. Spot clean the enclosure frequently, as you cannot have any ammonia start to build up, as there is no filter or cycle. The Methylene Blue will kill any bacteria that keep the cycle, so filters are useless.
Here we will cover the effects of nitrate poisoning, but betta fish kept in bowls often do not survive long enough to make it to this stage of the nitrogen cycle, so it is normally a nonissue.
Nitrates are by far the least toxic nitrogen compounds in the nitrogen cycle. It is safe in levels up to 40ppm, unlike ammonia and nitrite, which are toxic at any level.
Over time, nitrates negatively impact the immune system and life span of fish, leading to illnesses they would otherwise not have encountered, such as Hole in the Head disease. As you can probably imagine, this illness causes deep pits and holes in the head, normally along a lateral line.
Treatment is very difficult, as the medication must be administered orally, but this illness causes fish to lose their appetites.
High nitrate levels followed by a large water change can send fish into nitrate shock. Even if their environment is much improved, the sudden change from high nitrates to low nitrates will shock fish and possibly kill them.
If you have your nitrates build up to extreme levels, do several small water changes every day, about 10-15%. Keep this up until the nitrates drop down to a more manageable level.
Fitting filtration into a bowl is almost impossible and will take up necessary space. In addition, it is normally impossible to fit an appropriately sized filter into a bowl, so you will be left with high levels of ammonia and nitrite that will burn and suffocate your fish to death.
The best kind of filtration for bettas is a sponge filter, but you would be hard pressed fitting one into a bowl. Another option would be a Hang on Back (H.O.B.) filter, but these do not fit on the rounded edges of a tiny bowl.
A small canister filter may be an option, but it would likely be very difficult to fit a bowl and the flow would be far too strong. The last option is an internal filter, but bettas are frequently injured by these, and again, they will not work on a rounded rim.
So, maybe you could try a Walstad tank, or a dirted tank capped with sand and filtered by plants. Unless you have a 5-gallon bowl, you will never have enough plants to reduce the nitrogen compounds. Eventually, it will succumb to poisoning.
Heaters are another issue in small bowls, especially those without water movement or filtration, as the lack of circulation will unevenly heat the bowl. In addition, heaters will rapidly change the temperatures in such a small area, risking temperature shock and death.
That is, of course, if you are able to fit a heater in such a small area. If you are not, the fish will suffer. Bettas come from very warm regions and prefer their temperature between 78-82 degrees. Of course, they can survive slightly outside of this range, but they will be lethargic and open to disease.
If kept at an improper temperature, the fish are more likely to contract diseases. This is because they are a cold-blooded animal, meaning they cannot regulate their own temperature and are dependent on their environment.
In a cold environment, their immune system cannot work properly, leading to disease and other issues. While there may be slightly more dissolved oxygen present, their organs simply do not function well at lower temperatures.
Just like any fish, betta needs room to swim. No matter the size of their tank, from 40 gallons or 4, they will use all space given to them. They are an active fish, with the exception of those disabled by excessively long fins.
While you may be able to get away with keeping one such disabled fish in a 2.5 or 3 gallon tank, they really need at least 5 gallons to thrive. This provides more room for them to explore, more water to dilute their waste, enough dilution for the biological filter to function, and enough room for a heater, bubbler, and filter.
In conclusion, betta fish will not survive very long in bowls under 2.5 gallons. They will be constantly bombarded with toxins burning away at their skin and suffocating them with their own blood. They need at least a 2.5 gallon to survive but will not thrive without 5 gallons of water.