HomeCompare fishSlim betta vs Siamese fighting fish Slim betta vs Siamese fighting fish: can they live together? Verdict: With cautionThe Siamese fighting fish can be semi-aggressive or nip fins.The Slim betta can be semi-aggressive or nip fins.Both are comfortable at 24–30°C (75–86°F).A pH of 6.5–7.5 suits both.Minimum tank for the pair: 75 L (20 US gal)Side by sideSlim bettaSiamese fighting fishAdult size10 cm (3.9 in)6.5 cm (2.6 in)Minimum tank75 L (20 US gal)20 L (5 US gal)Temperature24–30°C (75–86°F)24–30°C (75–86°F)pH6.5–7.56.0–8.0Hardness5–15 dGH (89–268 ppm)5–19 dGH (89–339 ppm)TemperamentSemi-aggressiveSemi-aggressiveCommunity tankGoodGoodCare levelEasyEasyDietOmnivoreOmnivoreSpecies profilesSlim bettaBetta bellicaSiamese fighting fishBetta splendens