just wanted to maybe defend BettaCreek a tad.
yes, true, nice owners do not cramp their fish in 1 gal bowls, but for the betta breeder, we do not have room to house each fish individually in a minimum 5 gal tank - that could mean having over 100 tanks! As well, a majority of our fish are sold once they reach a certain age, so if the new keeper of the fish is knowledgeable, the fish will get a nice big home. It is unfortunate that many people buy bettas and stick them in tiny torture bowls. It is unfortunate that any mistakes are made with any fish, but we all have made them at some point or another. There should be some sort of license system in place for owning fish.... lol.
In regards to the 100% water changes. I have done both - 100% and partial, for my bettas that have yet to be upgraded to "real" tanks. the 100% change did not stress my fish any more than the partial changes as far as environment disruption (i did experiements doing 25%, 50% and 75%), but what i did notice was that the level of ammonia did not satisfactorily decrease with the 25 and 50 % changes, and was only a little better with the 75%. That being said, shouldn't we worry more about having our fish in clean water, especially in such a small environment? and as far as i know, there is no chance for good bacteria to develop if you are doing even a once weekly change on an unfiltered bowl anyway, so you are not really preserving anything by doing only a partial change.
This seems to be a bit of a heated thread. would like to know everybodys views.