Qui mi fermo perchè a questo punto non so risponderti.
Ti riporto quanto puoi trovare sul sito seriouslyfish.net (per l'esattezza l'indirizzo è questo:
http://www.seriouslyfish.com/profile...ndens&id=19#11)
Compatibility
There is some debate as to whether the species makes a good community fish or not. In general, we think it's best suited to a species tank. The elongated finnage of males is delicate and easily damaged, and some of the forms can find it difficult to compete for food with more vigorous tankmates. Males are also territorial and do better when given their own space. Females can be kept succesfully in quiet community tanks and tend to be happiest when maintained in groups of 6 or more.
If other species must be kept with fancy males, very peaceful, sedate species make the best tankmates. Possiblities include dwarf Corydoras, Otocinclus sp., and small shoaling species such as Trigonostigma or Boraras sp. Avoid any species with flowing finnage like guppies, as a male fighter may see these as competition and attack them.
Certainly, only one male should ever be kept per tank. If you want to keep females alongside one, it's best to buy a group so that no single female is subject to continual harassment from the male.
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Come vedi non sono tante le possiblità....e poi ripeto, quel sito cita i cory....ma anche loro come è stato dimostrato rischiano....
Se volessimo seguire queste linee guida del sito (che direi essere abbastanza attendibile) forse gli otocinclus sono i più economici e i più reperibili tankmates per il tuo betta....