What are frog-friendly medications?

[Emily in Everett]

Issue: planted tank with betta and african frogs. Betta's fins have suddenly started to degrade, suggesting fin rot (no obvious discoloration of edges but tissue between the rays is "melting back". We've had this with previous bettas and medication has stopped the melt and fins grew back. But those were betta-only tanks without frogs.

Question: what are medications I could use for the betta that would not be poisonous to frogs?

[Tihshho]

Are you able to pull the betta and treat it in a QT tank? You might be able to use more effective medication rather than find something that is safe with other tank mates.