I have more pet peeves than see myths in some cases..Based on my opinion, experience, logic, common sense, experiments and research of scientific data.
One of my biggest pet peeves-Is seeing the domesticated Long fin Betta being compared to their wild cousins-especially regarding care and housing or worse a Betta being compared to mammals. Fish in general, brains are not wired the same way and don't feel per se or at least the same as mammals.
Another is-All white poop is internal parasites-there are more internal parasites that don't have S/S of white poop than with it. Sometimes the fecal matter color change is diet or stress related and with females it can be egg related. All fish have some degree of internal parasites to start with and they keep them controlled themselves along with the immune response.
Shot gun treatment method is another one-Tossing all kinds of chemicals, pesticides, antifungal...etc...Without knowing what you are dealing with or understanding what these types of products can do to- not just the fish-but to us and the environment or how water quality and chemistry can change effectiveness of these types of products. Not to mention resistance that can be caused by over use, improper use...etc....
A big pet peeve I have too-is seeing members belittle other members because, either they don't agree with them or keep their Bettas like they do. Lots of different methods to properly keep this species. So much is based on the Betta itself in some cases-what works for me-might not work for you or you may not be able to get the same things that I can.
Viewing the poop as a piece of ammonia-Its just a turd until it breaks down-Most of the ammonia is excreted via the gills to start with and most water quality problems are due to poor quality fish food, overfeeding or leaving uneaten food long term-then from the Betta byproducts.
That gradual temp changes are stressful-Water temp normally changes gradually with light on/off, day/night and will have varied temps within the tank itself-these are normal, gradual changes that can vary up to 10 degrees in some cases-but it is slow. Its those sudden extreme changes that can be stressful and even fatal in some cases-especially on an already compromised Betta.
Changing the pH with chemical additives-most Betta will adjust to your source water pH-By changing the pH with chemicals without proper buffers can result in rebound and this can be stressful on the Betta-not to mention stressful for you and waste of money. Better to allow the Betta to adapt to your pH, however, there are some exception and pH might need to be adjusted-then you need to change the KH/GH with use of R/O water or adding crushed corral-what ever the case may be.
The nitrogen cycle being made to sound to complicated when its a natural process.
Pellets swell up in their stomach and while the pellets will swell up in water-the stomach contents of the Betta isn't water-its-bacteria, gastric acid and enzymes. If a Betta bloats due to food-it is most likely due to poor quality food that is high in grains/grain byproducts that create a gas as the bacteria break it down.
That peas will clog them up or are bad for them. The bacteria, enzymes and acids break it down, however, since a Betta has a short GI tract the pea passes too fast and since it takes longer for veggie matter to break down for the nutrients to be used-the pea doesn't provide adequate nutrients and shouldn't be used as a staple in the diet-but it is fine/safe to use short term for treatment.
That they can't be kept with guppies-especially fancy tail males because the Betta will confuse another male guppy as a Betta. They don't confuse species, however, most problems between other long fin fish and Bettas are usually due to space. Usually, neither the long fin male Betta or long fin guppy can swim very fast and are able to catch each other to fin nip-especially in smaller tanks-one or the other usually ends up with tattered fins because they can catch each other-not because they confuse species.
To expand on some already posted-
If you have a filter you don't need to change water as often. Out of sight-out of mind. Aquariums are closed systems and nothing leaves the tank until you remove it or the biological filter breaks it down. Debris is collected in the filter/filter media and is circulated over and over until the biofilter takes care of it. Clear water doesn't mean good or clean water pre se-it just mean its clear.
You may or may not need a heater, however, it is a good idea to have one on hand. Your goal is to maintain a somewhat stable temp of at least 75F for long term keeping.
Longevity-that the size of the tank makes a difference in how long the Betta lives. This is a short lived fish to start with-normal life span 2-3 years-rarely over 4-5yrs and in laboratory conditions over 7 years, however, there are exceptions-with some living beyond 5 years in home aquarium. This species is born, matures and reproduces within the first 3-6mo of life-mere seconds can make a difference in the fish world.
Water quality, poor nutrition and genetics have a bigger role in longevity than tank size.
Water quality is more important than tank size.
Water changes shouldn't be based on test alone, its a good starting point, however, due to other things in the water/tank that we don't test for that can be harmful on long term health-regular weekly/twice weekly water changes to maintain the system are recommend-exception of lots and lots of live active growing plants.
The natural chemistry changes that occur over time and when a long over due water change is made can cause a sudden extreme chemistry change that results in sick and/or dead fish-This is where one of the myths come from "A water change killed my fish"
When keeping the domesticated Long fin male Betta-(depending on age, genetics, how reared at the fish farm, how cared for at the pet shop, overall general health, nutrition and past health history)-
Sometimes the Long fin male will thrive best in smaller tanks without water movement-Not all will have problems, some will be fine short term in larger tanks and water movement. But some of the Long fin males can have special needs due to the man-made Long, heavy, delicate fins they carry around.
Sometimes the mere use of those long fins to swim in larger volumes of water and/or with water movement can be stressful and tatter fins. This stress can sometimes cause neurotic behaviors like glass surfing, tail biting, going off food. The stress alone can compromise the immune response. The space, using the fins to swim and/or water movement that causes the long delicate fins to tatter may only be cosmetic, however, the opening in the tissue-along with stress that compromise the immune response can set them up for a secondary infection that can snow-ball into something worse.
Remembering that often these Long fin males have never been kept in water volume greater than a few cups from the age of 6-10 weeks and rarely with any water movement-This is to grow out the unnatural long fins that some of us love and reason why we want them in the first place-beside the awesome personality some can have. By understanding these special needs-we might have to keep them in smaller tanks without filters in the beginning and slowly add them to larger spaces in steps.
It can be so frustrating for a new keeper to buy a beautiful Long fin Betta and then with good intentions-place them in a large filtered tank-only for the long fins to tatter or seem to love the big filtered tank for a week and they soon hide in a corner, stop eating and/or get sick-And the new hobbyist ask why or what did I do wrong-thinking they would love a lot of water to feel free-swim-play...etc....Its not really your fault and you didn't do anything wrong per se-By understanding the special needs of the Long fin male-you might have to go slow-in steps so they can tolerate the wide-open space....because a lot of the long fin males can be successfully kept in large filtered tanks-it just might take some time....
By understanding normal behavior-will help you understand abnormal behavior. Knowing how these behaviors can change or be different with age and different between males and females-This is so you won't stress out-then stress the Betta with unneeded treatments....