Actually the beatta's don't put up with those little cups all that well. While a fish without the ability to breathe air w might not last as long in an uncirculated cup, a fish such as a danio would last must longer in that amount of ammonia. Either way the fish in the ammonia would be damaged.
Run a search on threads for Beatta's with fin rot, fungus, and so on. The numbers are astronomical. Ammonia burns weaken and stress fish, Beatta's are not really that hardy to begin with. So while they may survive for a few days or even a couple of weeks in a cup, they usually end up dead pretty quickly when they go home.
A decent LFS will provide a slightly larger environment for them, and additionally will provide Frequent 100% water changes. Those beatta's will seldom have issue with Fin rot, or other fungal and bactrial ailments.
So in a nutshell, Ammonia does not cause fin rot, but it throws the door wide open and the end result is a dead or permanently damaged fish.
Have you ever wondered why people don't view Gourami's in the same light that they view beatta's in this discussion? It is only because gourami's will live together in a tank. If beatta's could co-exist we would see the eventual death of the beatta cups and some of the beatta myths.
In answer to your original question, Beatta's would be less useful for fishy cycling than many other fish. The advantage of the labirynth organ doesn't help them with ammonia issues only with low oxygen issues.
Dave
Run a search on threads for Beatta's with fin rot, fungus, and so on. The numbers are astronomical. Ammonia burns weaken and stress fish, Beatta's are not really that hardy to begin with. So while they may survive for a few days or even a couple of weeks in a cup, they usually end up dead pretty quickly when they go home.
A decent LFS will provide a slightly larger environment for them, and additionally will provide Frequent 100% water changes. Those beatta's will seldom have issue with Fin rot, or other fungal and bactrial ailments.
So in a nutshell, Ammonia does not cause fin rot, but it throws the door wide open and the end result is a dead or permanently damaged fish.
Have you ever wondered why people don't view Gourami's in the same light that they view beatta's in this discussion? It is only because gourami's will live together in a tank. If beatta's could co-exist we would see the eventual death of the beatta cups and some of the beatta myths.
In answer to your original question, Beatta's would be less useful for fishy cycling than many other fish. The advantage of the labirynth organ doesn't help them with ammonia issues only with low oxygen issues.
Dave
Agreed I'm a confirmed BioSpira fan also 
